LIBRARY 

OF  THE 

UNIVERSITY  OF  CALIFORNIA. 

Class 


THE    TELEGRAPHIC 

TRANSMISSION      OF 

PHOTOGRAPHS 


THE   TELEGRAPHIC 

TRANSMISSION     OE 

PHOTOGRAPHS 


T.   THORN E    BAKER, 

F.C.S.,  F.R.P.S.,  A.I.E.E. 


NEW  YORK 
D.   VAN    NOSTRAND    CO. 

23  MURRAY  AND  27  WARREN  'STREETS 

1910 


PREFACE 

VERY  little  is  known  at  present  about  the  telegraphy 
of  pictures,  because  -the  published  descriptions  of  the  * 
instruments  in  use  have  been  confined  almost  entirely 
to  technical  journals.  The  desire  to  have  news  at 
the  earliest  possible  moment,  and  the  recent  demand 
by  the  public  to  have  the  "  news  in  pictures,"  has 
opened  up  the  field  for  a  new  science,  which  is  a 
peculiar  mixture  of  electricity,  optics  and  photo- 
engraving. The  telegraphed  picture,  at  first  looked 
upon  as  a  marvel,  now  occasions  little  or  no  surprise, 
which  means  that  it  is  sufficiently  like  an  ordinary 
photograph  to  pass  muster  among  the  other  pictures 
in  the  newspaper  in  which  it  appears. 

During  the  last  two-and-a-half  yeajrs,  a  great  deal 
of  experimental  work  has  been  carried  out  by  me  for 
The  Daily  Mirror,  and  it  has  been  very  largely 
owing  to  the  active  interest  this  journal  has  shown 
in  photo-telegraphy  that  the  pioneer  work  in  this 
country  has  been  possible.  The  interest  displayed 
in  the  work  by  the  editor,  Mr.  Alex.  Kenealy,  has 
never  failed,  and  to  his  encouragement  and  enter- 
prise the  present  position  of  this  new  branch  of 
telegraphic  work  is  largely  due. 

210719 


vi  PREFACE 

The  descriptions  given  in  the  book  of  the  systems 
in  use  to-day  will,  I  hope,  make  quite  clear  to  the 
reader  "  how  it  is  done."  Though  certain  portions 
of  the  matter  are  intended  for  those  already  con- 
versant with  the  general  principles  of  electricity,  the 
bulk  of  the  book  has  been  written  as  simply  as 
possible,  and  if  the  said  portions  are  just  passed  over 
by  the  non-technical  reader,  I  think  the  rest  will  be 
of  interest  to  him. 

At  the  time  of  going  to  press,  preparations  are 
being  made  for  an  endeavour  to  transmit  photographs 
by  wireless  telegraphy  across  the  Wash,  the  Post- 
master-General having  courteously  allowed  me  the 
use  of  the  experimental  wireless  stations  at  Hun- 
stanton  and  Skegness.  The  last  chapter,  therefore, 
dealing  with  wireless  work,  will  make  the  reader 
acquainted  with  the  latest  phase  of  photo-telegraphic 
work. 

T.    THORNE    BAKER 

15,  GROSVENOR  GARDENS, 

CRICKLEWOOD,  N.W., 

March,   1910. 


CONTENTS 


PAGE 

PREFACE        .         .         .         .         .         .         .         .         .         .     v 

LIST  OF  ILLUSTRATIONS       .  .    ix 


CHAPTER   I. 

Attempts  at  the  Solution  of  the  Telegraphic  Transmission  of 
Photographs  and  Pictures p.  i 

CHAPTER    II. 

Professor  Korn's  Selenium  Process — Early  Work  with  his 
Original  Receiver  —  The  String  Galvanometer  —  Syn- 
chronism— First  Experiments — The  Early  History  of 
Commercial  Photo-Telegraphy  .  .  .  .  p.  2,2, 

CHAPTER   III. 

The  Korn  Telautograph — Principles  of  Working — Advantages 
over  Selenium— Early  Work  with  Line  Pictures — Experi- 
ments with  Telephone  and  Telegraph  Cables — Recent 
Progress  with  the  Telautograph  .  .  .  .  p.  61 

CHAPTER   IV. 

The  Thorne- Baker  System — Differences  between  the  Telectro- 
graph  and  Earlier  Chemical  Systems  —  Electrolytic 
Records  of  Currents  Transmitted  through  Long  Cables  — 
The  Thome-Baker  Line-balance — Work  with  the  Electro- 
lytic Telectrograph p.  88 


viii  CONTENTS 

CHAPTER   V. 

Considerations  of  the  Telephone  and  Telegraph  Lines  and 
their  Influence  on  Photo-Telegraphy       .         .         .  p.  108 

CHAPTER   VI. 

The  Telestereograph  of  M.  Belin— The  Early  Work  of  Belin 
— Changes  in  his  System — Recent  Experiments      .  p.  116 

CHAPTER   VII. 

The  Transmission  of  Photographs  and  Pictures  by  Wireless 
Telegraphy p.  127 


INDEX 143 


LIST    OF    ILLUSTRATIONS 


FULL   PAGE   ILLUSTRATIONS. 

A  part  of  the  Daily  Mirror  Installation,  showing  the 
Korn  Telautograph  and  the  Thorne- Baker  Telec- 
trograph  .......  Frontispiece 

Receiving  a  photograph  on  the  Telectrograph  .    Opposite  p.  100 

ILLUSTRATIONS    IN    TEXT. 

FIG.  PAGE 

1.  Diagram  of  Bakewell's  instrument      ....  3 

2.  Section  of  a  film,  showing  silver  deposit     ...  13 

3.  Bernochi's  wireless  apparatus     .....  15 

4.  Polarisation  receiver  of  Rignoux  and  Fournier  .         .  17 

5.  Diagram  of  selenium  cell 22 

6.  Photograph  of  selenium  cell 23 

7.  Diagram  of  Korn's  selenium  transmitter    ...  24 

8.  Inertia  curve  of  selenium 27 

9.  Curve  showing  effect  of  light  on  selenium  ...  28 

10.  Korn's  compensating  bridge 29 

11.  Curve  showing  compensation  of  inertia      ...       30 

12.  Curve  showing  compensation  of  inertia      ...       30 

13.  Curve  showing  over-compensation      .         .         .  31 

14.  Section  of  Korn's  galvanometer .  -33 

15.  Section  of  interior  of  galvanometer     .         .  -34 

1 6.  Korn's  receiving  apparatus          .         .         .         .         -37 

17.  Photograph  of  a  galvanometer  as  used  by  Prof.  Korn       38 

1 8.  Diagram  showing  synchronising  arrangement    .        .       39 

19.  Diagram  of  friction  clutch  ...  41 

20.  Photograph  of  the  frequency  meter    .  -43 

21.  Diagram  of  switchboard  connections .  .       44 

22.  Prof.  Korn  at  the  telephone,  when  awaiting  the  first 

picture  from  Paris  in  1907       .  .       46 


LIST    OF    ILLUSTRATIONS 


23.  Curve  of  selenium  cell                                                     .  47 

24.  One  of  the  first  photographs  wired  by  Korn's  com- 

pensated selenium  machines  ...  -49 

25.  Photograph    of    King    Edward,    wired    to    London 

November  yth,  1907         .                                             .  50 

26.  Photograph  showing  induction  effects                  .         .  53 

27.  Example  of  a  news  photograph  sent  from  Paris          .  55 

28.  Diagram  illustrating  principle  of  the  telautograph      .  62 

29.  Korn's  telautograph  transmitter .                                   .  63 

30.  Diagram  of  stylus  holder 65 

31.  Diagram  of  Korn  telautograph    ...  -67 

32.  Diagram  of  synchronising  arrangement      ...  70 

33.  Wiring  of  reverser 71 

34.  Reception    to    Sven    Hedin,   wired    from    Paris    to 

London  by  Telautograph 75 

35.  Example    of    Fashion    Plate    wired    by    the    Korn 

Telautograph 77 

36.  Diagram  showing  duplex  transmission        .         .         -79 

37.  Line  drawing  transmitted  by  Telautograph         .         .  81 

38.  Example  of  line  sketch  from  photograph,  wired  by 

the  Korn  Telautograph  from  Paris  to  London       .  83 

39.  Damping  of  oscillograph  string 85 

40.  Example  of  half-tone  photograph  transmitted  from 

Berlin  to  Paris  by  Telautograph     ....  86 

41.  Telectrograph  tracing  stylus 91 

42.  Curve  showing  charge  and  discharge  of  a  cable         .  92 

43.  Diagram  of  connections  of  line  balancer    ...  93 

44.  Photograph   showing  the    balancing    effect    of    the 

Telectrograph  arrangement 94 

45.  Portrait  of  first  lady  councillor  of  Liverpool.     Wired 

by     the     Telectrograph     from      Manchester    to 

London 98 

46.  Portrait   of  Mr.   Howarth,  telegraphed   from   Man- 

chester to  London  by  the  Thorne- Baker  Telectro- 
graph       .                                    ioo 

47.  Half-tone  single  line  negative  image,  as  ordinarily 

used  for  the  Telectrograph      .         .         .         .         .102 

48.  Finish  of  the  St.  Leger,  wired  by  the  Telectrograph  .  104 


LIST    OF    ILLUSTRATIONS  xi 


49.  M.  Riolle,  Public  Prosecutor  in  the  Steinheil  case  ; 

wired  from  Paris  to  London  by  the  Thorne- Baker 
Telectrograph  .  .  106 

50.  News  photograph  wired  from  Manchester  to  London 

of  a  railway  accident  at  Staly bridge        .         .         .107 

51.  Apparatus  used  to  record  oscillograph  work       .         .     109 

52.  Oscillograph   record    of    half-tone    image    with    no 

capacity  on  line       .  ...     no 

53.  The  same  with  capacity,  showing  the  elongation  and 

widening  of  the  "  teeth "          .         .         .  .     no 

54.  Section  of  a  relief  photographic  film  .         .         .         .117 

55.  Diagram  of  Belin's  transmitter   .         .         .         .         .118 

56.  Photograph  transmitted   by  M.    Belin's  Telestereo- 

graph,  over  an  artificial  line    .....     124 

57.  Belin's  apparatus  for  telegraphing  line  pictures          .     125 

58.  Diagram  of  wireless  apparatus 130 

59.  Diagram  of  Marconi's  Electromagnetic  Detector       .     132 

60.  Arrangement  first  used  by  the  Author  for  the  wireless 

transmission  of  pictures .         .         .         .         .  133 

61.  Sketch  of  head  and  shoulders  of  a  lady.      Trans- 

mitted by  wireless 135 

62.  Diagram  of  the  author's  decoherer     ....     136 

63.  Quartz  string   and   selenium   cell   arranged   for  re- 

ceiving and  transforming  up  electrical  oscillations  .     138 

64.  Sketch   of  the   King  transmitted    by   the    author's 

wireless  apparatus  .......     139 


THE   TELEGRAPHIC 
TRANSMISSION  OF  PHOTOGRAPHS 


CHAPTER    I. 

ATTEMPTS  AT  THE  SOLUTION  OF  THE  TELE- 
GRAPHIC TRANSMISSION  OF  PHOTOGRAPHS 
AND  PICTURES. 

THE  problem  of  transmitting  a  sketch  or  photo- 
graph over  a  distance  by  means  of  electricity  has 
occupied  the  minds  of  many  engineers  and  scientists 
for  the  past  sixty  years,  but  it  has  been  up  to  the 
present  time  a  singularly  ungrateful  task,  owing  to 
the  lack  of  possible  application.  The  tendency  for 
modern  journals  to  be  illustrated  with  photographs 
has  very  greatly  widened  the  scope  for  an  instru- 
ment by  which  they  can  be  "  wired/'  and  it  is  pro- 
bably for  this  reason  that  so  much  attention  has  of 
late  been  devoted  to  this  new  science. 

It  seems  difficult  on  first  thought  to  conceive  how 
a  picture  can  be  telegraphed.  But  a  picture,  just 
like  a  written  message,  can  be  split  up  into  com- 
ponent parts  ;  the  letters  forming  a 'word  have  a 
distinct  meaning  when  seen  assembled  together  in 

P.T.  B 


2  PHOTO-TELEGRAPHY 

proper  order,  while  the  dots  and  dashes  forming  a 
letter,  according  to  the  Morse  code,  possess  simi- 
larly an  intelligent  meaning  when  grouped  together 
in  correct  order  ;  by  building  up  a  complete  picture 
with  dots  or  small  areas  of  varying  depth,  size, 
or  density  we  can  produce  a  picture  in  a  strictly 
comparable  manner.  One  ingenious  attempt  at  the 
solution  of  photo -telegraphy — as  ingenious  as  it  is 
impracticable — has  been  to  divide  up  a  picture  into 
thousands  of  small  parts,  representing  each  by  a 
certain  letter  of  the  alphabet,  according  to  its  den- 
sity ;  thus  a  light  part  might  be  called  C  or  D,  a 
dark  part  Y  or  Z,  and  so  on.  The  letters  are  tele- 
graphed to  an  operator,  who  forms  a  fresh  picture 
by  building  it  up  with  small  "  parts/'  whose 
densities  are  in  accordance  with  the  respective 
letters.  Such  a  system  is  indeed  possible,  but  would 
require  a  very  great  amount  of  time.  It  is  the 
minutes  and  seconds  which  have  to  be  saved  in 
telegraphing  a  picture — especially  in  these  days  of 
rapid  railway  transit,  where  photographic  plates  can 
be  sent  to  the  newspaper  office  in  a  few  hours, 
so  that  only  very  late  events  are  telegraphed. 

This  book  is  not  intended  to  be  historical,  and  I 
shall  therefore  refer  only  to  such  early  processes  as 
have  a  direct  bearing  upon  the  work  that  is  being 
done  to-day.  Of  early  attempts  at  the  transmission 
of  pictures,  the  Bakewell  system  deserves  particular 
notice,  since  upon  it  is  based  one  of  the  three 


BAKEWELL'S    PROCESS  3 

most  successful  modern  methods  of  transmission. 
Bakewell's  machine,  which  created  some  attention 
as  far  back  as  1847,  consisted  of  two  synchronously 
revolving  metal  cylinders — one  at  each  end  of  the 
telegraph  lines,  over  each  of  which  a  metal  style 
traced  a  spiral  path  (in  the  manner  of  the  modern 
phonograph).  Upon  one  cylinder  was  placed  a 
sheet  of  tinfoil  with  the  sketch  drawn  in  ink  made 
with  shellac,  and  on  the  receiving  drum  was  placed 
a  sheet  of  paper  prepared  chemically,  so  that  on 

Battery 


FIG.  i. 

passing  an  electric  current  through  it  a  chemical 
mark  or  stain  was  made.  It  appeared  as  seen  in 
Fig.  i  in  its  simplest  form.  A  and  B  represent 
the  two  cylinders,  tracing  over  which  are  shown 
two  styles.  A  battery  is  in  the  circuit.  It  will 
be  readily  seen  that  when  a  line  in  the  sketch 
which  consists  of  shellac,  comes  under  the  style  of 
A,  the  current  flowing  through  the  circuit  will  be 
broken,  whereas  when  the  bare  tinfoil  lies  between 
style  and  cylinder  the  current  will  flow. 

This  current  therefore  flows  intermittently 
through  the  chemically -prepared  paper  attached  to 
the  drum  /?,  and  when  it  flows,  it  causes  a  chemical 


4  PHOTO-TELEGRAPHY 

mark  on  the  paper.  Hence,  when  the  style  has 
traced  over  the  entire  length  of  the  sketch  at  A,  the 
latter  will  be  reproduced  (negatively)  at  B.  By 
suitable  means  it  can,  of  course,  be  received  posi- 
tively if  desired. 

Such  is  the  system  which  is  now  over  sixty  years 
old,  and  many  trials  were  made  with  it  to  telegraph 
writing  over  distances  ;  here,  however,  the  diffi- 
culties met  with  in  long  cables  were  at  once  felt  ; 
attempts  were  actually  made  at  one  time  in  France 
to  use  such  a  system  commercially,  but  they  were 
soon  abandoned. 

Thence  onwards  continuous  attempts  were  made 
to  solve  the  problem  of  transmitting  sketches, 
pictures,  and  photographs  ;  a  long  list  of  names  of 
these  early  workers  might  be  given.  But  we  may 
well  confine  our  attention  at  present  to  two  men, 
Amstutz  and  Shelford  Bidwell,  as  the  ideas  of  these 
men  were  actually  the  germs  of  two  important  pro- 
cesses which  have  now  given  most  satisfactory 
results.  The  latter  made  use  of  the  newly  dis- 
covered sensitiveness  to  light  of  the  metal  selenium, 
the  former  of  the  possibility  to  use  the  relief  in  a 
certain  form  of  photographic  image  to  vary  the 
strength  of  the  electric  current. 

On  the  lines  followed  by  Bidwell,  Ayrton  and 
Perry  also  made  experiments,  both  therefore  utilis- 
ing selenium  at  the  sending  station.  Let  us  suppose 
that  a  portrait  is  to-be  telegraphed  from  this  station 


THE    SELENIUM    CELL  5 

to  a  distant  receiving  station.  t  The  portrait  is  pro- 
jected on  to  a  screen,  where  light  and  shade  and 
varying  tones  are  produced.  Now  suppose  this 
screen  divided  up  into  a  thousand  square  sections, 
each  one  the  size  of  a  selenium  "  cell,"  the  cell 
being  an  arrangement  made  with  selenium,  which 
varies  in  its  electrical  resistance  according  to  the 
strength  of  the  light  illuminating  it.  This  cell  is 
held  in  one  section  of  the  bright  image  on  the 
screen,  then  in  the  next,  then  in  the  next,  and  so 
on,  until  finally  it  has  been  held  in  the  whole  thou- 
sand sections.  But  each  section  is  of  a  different 
brightness,  according  to  what  portion  of  the  image 
is  projected  upon  it.  In  each  section,  therefore, 
that  the  cell  was  held,  its  electrical  resistance 
varied. 

Now  imagine  you  could  record  these  variations 
in  resistance  on  a  similar  screen  at  the  receiving 
station.  When  the  selenium  cell  was  held  over 
section  i  of  the  image  of  the  screen,  its  resistance 
was,  let  us  say,  r\ ;  using  a  battery  of  100  volts, 
and  neglecting  the  resistance  of  any  connecting 
lines,  the  current  at  the  receiving  station  would  be 

— .       Let    this    regulate,    in    any    imaginable   way, 
r\ 

the  strength  of  an  electric  light,  which  is  shining 
on  a  similar  screen  at  the  receiving  station,  on  the 
screen  being  placed  a  sheet  of  sensitive  photo- 
graphic paper.  Next  let  the  selenium  cell  be  held 


6  PHOfO-TELEGRAPHY 

in  the  section  2,  so  that  a  slightly  different  part 
of  the  image  falls  upon  it,  the  resistance  changing 
to  r2,  and  the  current  at  the  receiving  station  to 

-  ;    simultaneously   let    the    electric  lamp  (whose 
Yi 

brilliance  has  of  course  changed  in  the  proportion 
of  r\  to  r2),  shine  on  section  2  of  the  receiving 
screen.  If  you  can  imagine  this  procedure  to  be 
carried  out  over  the  whole  photograph  at  the  send- 
ing station,  the  ever-varying  electric  lamp  being 
shone  on  always  corresponding  sections  of  the 
photographic  paper  at  the  receiving  station,  the 
movements  being  in  all  cases  synchronous,  you  will 
be  able  to  see  that  on  developing  the  sheet  of  papei 
a  photograph  would  be  obtained,  consisting  of  a 
thousand  square  patches  of  different  intensity, 
which,  examined  from  a  distance,  would  give  a 
representation  of  the  original  image  projected  on 
the  screen.  Such  a  process  would  in  practice  be 
both  absurd  and  impossible,  but  it  enables  one  to 
form  some  conception  of  the  idea  of  Bidwell  and 
Ayrton  and  Perry. 

The  image  to  be  telegraphed  could  quite  easily 
be  a  photograph  printed  on  a  transparent  material, 
such  as  celluloid,  and  this  print  fixed  to  a  revolv- 
ing glass  cylinder,  inside  which  was  fixed  an 
electric  lamp,  whose  rays  were  concentrated  so  as 
to  pass  through  one  spot  on  the  cylinder  to  a  fixed 
selenium  cell.  On  then  revolving  the  cylinder 


SELENIUM    DIFFICULTIES  7 

and  letting  it  also  rise  spirally,  the  pencil  of  light 
would  traverse  different  consecutive  parts  of  the 
picture,  and  the  light  falling  on  the  selenium  would, 
of  course,  vary  in  strict  accordance.  Such  a 
method  is  practically  similar  to  that  actually  used 
by  Professor  Korn,  as  will  be  seen  on  reading  the 
next  chapter. 

Then,  again,  the  current  sent  to  the  receiving 
station,  which  would  depend  at  each  instant  on  the 
density  of  the  particular  piece  of  photograph 
through  which  the  pencil  of  light  was  passing,  could 
be  utilised  to  open  or  close  a  shutter  through  which 
another  pencil  of  light  could  be  admitted  to  a  sen- 
sitive photographic  film.  Suppose  this  film  on  a 
cylinder  revolving  in  a  precisely  similar  fashion  to 
the  transmitting  cylinder,  and  you  have  what  prac- 
tically amounts  to  Professor  Korn's  receiver. 

The  great  practical  difficulty  arose,  however, 
from  the  fact  that  selenium,  unlike  the  feminine 
mind,  could  not  change  rapidly  enough  ;  there  are 
an  immense  number  of  different  tones  in  one  small 
strip  of  a  photograph,  and  the  constant  changes  in 
illumination  were  not  at  all  well  responded  to  by 
the  selenium  cell .  The  practical  application  of  the 
method  was  destined  to  await  Professor  Korn's  re- 
markably ingenious  work  on  the  compensation  of 
the  "  lag  "  in  selenium  cells,  which  only  became 
possible  after  much  very  ingenious  mathematical 
and  experimental  work,  Korn  is  a  master  mathe- 


8  PHOTO-TELEGRAPHY 

matician,  and  photo -telegraphy  is  one  instance 
where  somewhat  abstruse  calculations  on  paper 
turned  out  to  be  in  perfect  harmony  with  practical 
work. 

In  referring  to  the  methods  of  Amstutz,  I  will 
quote  from  an  interesting  article  by  Mr.  William 
Gamble,  that  appeared  twelve  years  ago  in  the  first 
number  of  Penrose's  Pictorial  Annual,  of  which  he 
is  the  editor.  Briefly,  he  says,  the  process  is  this  : 
A  photograph  in  relief  (prepared  in  gelatine)  is 
fixed  to  something  akin  to  a  phonograph  cylinder, 
so  that  a  stylus  travels  over  its  surface,  rising  and 
falling  as  the  picture  passes  beneath  it.  Instead 
of  producing  sound,  like  the  phonograph,  it  is  made 
to  vary  the  strength  of  an  electric  current,  which 
passes  over  a  telegraph  wire  and  actuates  a  similar 
stylus  at  the  other  end,  which,  bearing  on  a  plate 
bent  round  a  revolving  cylinder,  cuts  a  reproduc- 
tion of  the  original,  but  in  a  series  of  parallel  lines 
(the  successive  "  turns  "  of  the  cylinders)  which 
gives  the  effect  of  a  half-tone  block.  The  stylus  is 
sharpened  like  a  graving  tool,  V-shaped,  so  that 
as  it  cuts  deeper  it  cuts  wider,  and  in  printing 
produces  darker  or  wider  lines, 

Amstutz,  in  a  lengthy  letter  which  the  editor  of 
the  Annual  publishes,  describes  a  method  in  which 
a  photographic  print  is  made  on  a  metallic  sheet, 
the  half-tone  of  the  photograph  being  broken  up 
into  parallel  lines,  "  the  photo -message  being  re- 


AMSTUTZ   AND    BELIN  g 

ceived  at  the  distant  station  in  an  engraved  manner 
ready  for  printing." 

"  Theoretically/'  he  says,  "  the  half-tone  system 
encounters  no  difficulties  whatever.  From  a  prac- 
tical point  it  is  not  available  for  commercial  work." 
He  describes  the  troubles  that  would  arise  from 
interference  effects,  owing  to  the  lack  of  correspon- 
dence that  there  would  be  between  the  mesh  of  the 
half-tone  screen  and  the  path  travelled  by  the  stylus 
over  the  cylinder,  and  claims  that  by  using  the 
single-line  pictures  referred  to  these  troubles  could 
be  avoided. 

In  all  the  half-tone  photo -telegraphic  work 
single -line  pictures  are  solely  used,  but  at  present 
no  satisfactory  method  has  been  obtained  of 
engraving  the  block  direct  during  the  reception. 

Amstutz's  idea  of  using  a  photographic  image  in 
relief,  and  making  the  actual  relief  mechanically 
vary  an  electrical  resistance,  has  been  successfully 
followed  up  by  a  French  inventor  named  Belin,  but 
he  again  cannot  obtain  direct  engraving  at  the 
receiving  end. 

Direct  photo  -  engraving  by  telegraphy  may 
"come"  some  day,  but  not  until  that  much  desired 
thing  has  been  discovered,  the  variable  relay.  The 
resistance  of  a  telephone  line  two  hundred  miles 
long  may  be,  perhaps,  2,000  ohms.  We  cannot 
employ  very  high  voltages,  100  volts  being  con- 
sidered very  high  ;  if  we  divide  i  oo  by  2,000,  we 


io  PHOTO-TELEGRAPHY 

get  the  maximum  amount  of  current  that  could  be 
obtained  at  the  receiving  station — one -twentieth  of 
an  ampere ;  with  '05  ampere  and  only  therefore 
5  watts,  it  would  be  almost  impossible  to  actuate 
a  graving  tool,  even  to  cut  into  some  soft  composi- 
tion. Block -making  is  so  rapidly  done  in  a 
modern  illustrated  newspaper  office  that  such  a 
method  is  not  now  worth  following  up. 

Turning  next  to  Caselli's  pan-telegraph,  we  find 
him  employing  a  sheet  of  metal  with  a  sketch  or 
writing  drawn  upon  it  in  insulating  ink  ;  the  sketch 
on  metal  was  stretched  over  a  curved  copper  plate, 
and  a  similar  curved  plate  was  placed  at  the  receiv- 
ing station,  a  sheet  of  paper  moistened  with 
potassium  ferricyanide  solution  being  stretched 
over  it.  The  plates  were  electrically  rocked, 
synchronism  being  obtained  by  means  of  a  pen- 
dulum. A  metal  stylus  traced  over  the  sketch  at 
one  end  and  over  the  paper  at  the  other,  the  circuit 
being  completed  through  the  metal  plates.  At  the 
end  of  each  "  rock  "  the  paper  and  sketch  were 
shifted  laterally,  so  that  in  each  case  the  stylus 
travelled  over  a  line  parallel  to  the  last  line  traced. 
When  the  sending  style  touched  the  metal  the 
current  flowed  and  the  ferricyanide  was  decom- 
posed, a  blue  mark  being  produced.  Some  excel- 
lent transmissions  of  writing,  etc.,  were  obtained 
in  this  way  at  a  comparatively  high  rate  of  speed. 
The  same  system  was  employed  by  the  French  tele- 


THE   TELEWRITER  n 

graph  engineer,  Meyer,  except  that  he  used  syn- 
chronously revolving  cylinders  in  place  of  the 
curved  metal  plates. 

Although  the  transmission  of  writing  cannot  be 
classed  with  the  telegraphy  of  photographs,  it  will 
be,  nevertheless,  of  interest  to  describe  the  tele- 
writer, which  gives  a  facsimile  reproduction  at  the 
receiving  station  of  anything  written  or  sketched 
at  the  sending  station.  In  writing  any  letter  on 
paper,  the  movement  of  the  pen  can  always  be  re- 
solved into  horizontal  and  vertical  components  ; 
by  making  these  resolved  movements  mechanically 
vary  two  resistances,  currents  of  two  corresponding 
strengths  can  be  transmitted  to  a  receiving  instru- 
ment ;  but  three  lines  are  necessary,  or  two  lines 
and  an  earth.  The  two  currents  when  received  are 
used  to  actuate  a  V-shaped  nib  filled  with  ink,  both 
vertically  and  horizontally,  the  resultant  move- 
ment causing  the  nib  to  trace  over  the  paper  a 
replica  of  whatever  the  transmitter  draws  with  his 
mechanical  "  pen."  In  the  telautograph  of  Grzanna, 
the  two  currents  corresponding  to  the  vertical  and 
horizontal  movements  of  the  transmitting  pen  are 
made  to  actuate  a  mirror  galvanometer,  the  mirror 
of  which  can  turn  about  two  axes,  so  that  a  spot 
of  light  traces  the  letters  or  sketch  over  a  sheet 
of  photographic  paper. 

^These  methods  are  only  suitable  for  transmitting 
sketches  or  designs  that  are  drawn  at  the  actual 


12  PHOTO-TELEGRAPHY 

time  of  transmission.  A  cartoon  was  in  one 
instance  drawn  by  Mr.  W.  K.  Haselden  in  Man- 
chester and  sent  by  him  to  the  London  office  of 
the  Daily  Mirror,  but  it  was  not  so  satisfactory  as 
the  same  sketch  would  have  been  had  it  been 
photographed  and  then  telegraphed  to  London  ; 
the  pencil  of  the  transmitter  requires  some  prac- 
tice to  use  it  with  comfort. 

A  method  more  recently  worked  out  for  the 
transmission  of  photographs  is  that  of  Charbonelle, 
a  French  postal  engineer,  in  which  once  again  the 
Caselli  transmitter  is  employed,  and  a  series  of  short 
currents  are  transmitted  which  correspond  to  the 
interruptions  caused  by  the  insulating  lines  of  a 
sketch  or  single -line  screen  half-tone  photograph. 
He  has  also  endeavoured  to  transmit  by  a  method 
that  has  been  put  to  the  test  by  almost  every 
engineer  who  has  paid  any  attention  to  the  problem 
of  photo -telegraphy,  namely,  by  causing  the  deposit 
of  silver  (or  other  substance)  in  the  image  of  a 
photographic  film  to  act  as  the  means  of  varying 
the  current  transmitted'.  This  was  very  carefully 
investigated  by  the  author  in  1907,  about  a  year 
before  the  publication  of  Charbonelle's  patent,  but 
although  results  of  a  kind  were  obtained,  the  idea 
was  abandoned  owing  to  certain  fundamental  diffi- 
culties which  will  probably  never  be  overcome. 

In  Fig.  2  is  seen  a  diagrammatic  representation 
of  a  transverse  section  of  the  film  of  an  ordinary 


CONDUCTIVITY   OF    FILMS  13 

photographic  negative.  Let  S  be  a  stylus  travel- 
ling over  the  film  ;  now  consider  any  points 
PQR,  it  being  supposed  that  the  film  has  been 
coated 'on  metal  foil  instead  of  glass  or  celluloid. 
If  one  terminal  of  a  battery  be  connected  to  S,  the 
other  to  the  metal  foil,  current  will  flow  from  S  to 
P,  in  one  instance  the  reduced  silver  grains  form- 
ing the  image  being  represented  by  dots.  Now 
suppose  the  stylus  to  be  at  S',  where,  owing  to  a 
light  part  of  the  picture,  there  is  much  less  deposit 
of  silver.  Assuming  trie  film  to  be  of  gelatine  (in 
a  moist  condition), 
less  current  will  ,s  -s' 

ir  ,>, 

flow  from  S'  to  R  **p~'~"'':' "'-'    ::?"  ':'^ 

than    from     S    to  "p q ^ 

P,    as    between  S  FIG.  2. 

and    P   there    are 

many  more  granules  of  silver  to  render  the  film 
more  conductive.  Hence,  if  the  photograph  be 
rotated  on  a  cylinder,  and  the  stylus  trace  a  spiral 
path  over  its  surface,  the  current  flowing  through  it 
to  a  receiver  should  vary  in  accordance  with  the 
depth  of  silver  deposit.  I  also  tried  using  a  relief 
carbon  image  on  copper  foil,  the  gelatine  being 
saturated  with  a  badly  conducting  medium,  so  that 
the  current  passing  from  style  to  copper  base  would 
vary  inversely  as  the  thickness  of  the  film  ;  some 
fair  results  were  obtained  in  this -way,  but  the 
method  would  be  always  very  uncertain,  as  the 


14  PHOTO-TELEGRAPHY 

current  would  pass  through  the   film  in  the  line 
of  least  resistance. 

Charbonelle's  receiver  is  also  one  that  has  been 
suggested  by  some  of  the  earlier  workers  ;  he 
passes  the  received  current  into  a  microphone,  in 
the  centre  of  the  diaphragm  of  which  is  a  hardened 
point  ;  this  point  of  course  vibrates  in  the  same 
manner  as  the  diaphragm.  The  microphone  is 
brought  down  over  the  cylinder  of  the  receiving 
apparatus  until  it  presses  on  an  outer  sheet  of  paper 
wrapped  round  it  ;  under  this  outer  paper  is,  first, 
a  sheet  of  carbon  paper,  and  second,  another  sheet 
of  plain  paper.  As  the  microphone  diaphragm 
vibrates  in  response  to  the  interruptions  of  the 
current,  so  the  point  digs  into  the  outer  paper  and 
the  mechanical  pressure  causes  a  carbon  mark  on 
the  inner  paper.  The  results  are  stated  to  be  good, 
but  the  method  is  not  likely  to  be  of  use  for  long 
distances. 

Berjonneau  has  worked  out  a  method  of  trans- 
mitting half-tone  photographs  made  with  a  single  - 
line  screen,  the  receiver  containing  a  minute  shutter 
which  cuts  off  or  allows  to  pass  the  rays  from  a  lamp 
concentrated  on  a  revolving  sensitive  film.  I  Have 
seen  a  promising  result  obtained  with  his  appa- 
ratus,* but  detailed  particulars  of  his  system  are 
not  yet  available.  He  has,  however,  made  trans- 
missions over  a  telegraph  line  from  Paris  to  Eng- 
*  Shown  at  Soc.  Ing.  Civ.,  Paris. 


A    WIRELESS    METHOD  15 

hien  "  in  four  minutes  seven  seconds,"  according 
to  a  newspaper  report,  "  and  the  reproduction  at 
EngHien  did  not  show  any  signs  of  lines,  and  might 
have  been  made  in  the  studio  of  a  photographer.1' 

An  ingenious  idea  for  transmission  without  wires 
deserves  mention  here,  and  has  been  patented  by 
the  inventor,  Francesco  de'  Bernochi,  of  Turin.  The 
invention  can  never  be  of  much  practical  value,  and 
is,  in  fact,  a  retrograde  one,  carrying  us  back  to  the 
early  experiments  in  wireless  telephony  by  means 


FIG.  3. 

of  light  waves.  The  apparatus  can  be  followed  by 
glancing  at  Fig.  3.  Here  Ci  is  a  glass  cylinder 
with  a  transparent  photographic  film  wrapped  round 
it,  and  light  from  the  lamp  L,  after  passing  through 
a  small  portion  of  it,  is  reflected  by  a  prism  on  to 
a  selenium  cell  SS.  This  is  in  series  with  a  battery 
and  the  primary  of  a  form  of  induction  coil.  As 
light  of  different  intensities  falls  on  the  selenium 
cell,  whose  resistance  alters  in  proportion,  current 
is  induced  in  the  secondary  of  the  coil  and  influ- 
ences an  arc  lamp,  on  whose  circuit  it  is  shunted  ; 


16  PHOTO-TELEGRAPHY 

this  arc,  the  poles  of  which  are  represented  in  the 
diagram  by  PP,  is  placed  at  the  focus  of  a  parabolic 
reflector  RI,  and  its  rays  are  therefore  reflected  as 
a  parallel  beam  to  the  receiving  reflector  R2.  At 
the  focus  of  this  second  reflector  is  a  selenium  cell 
Z,  whose  resistance  is  altered  by  the  light  falling 
upon  it  from  the  reflector.  This  cell  is  in  series 
with  a  battery  and  mirror  galvanometer,  light  from 
a  lamp  N  being  reflected  by  the  mirror  on  to  a 
graduated  aperture  H  ;  the  collected  light  is 
focussed  upon  a  photographic  film  attached  to  the 
drum  €2,  which  revolves  synchronously  with  the 
transmitting  cylinder  Ci. 

The  idea  is  an  ingenious  one,  and  might  be  made 
to  work  in  practice  over  distances  of  a  few  hundred 
yards,  but  not  more.  A  suggestion  was  made  on 
somewhat  similar  lines  to  these  to  the  author  by 
Mr.  Sharman,  in  reference  to  Korn's  selenium 
machines,  but  for  the  purposes  of  wireless  tele- 
graphy the  fluctuations  in  the  resistance  of  the 
selenium  would  be  used  to  influence  the  undamped 
oscillations  given  out  by  a  singing  arc,  and  a  suit- 
able receiver  would  record  these  fluctuations 
photographically . 

One  other  possible  means  of  receiving  from  any 
form  of  transmitter  over  short  distances  deserves 
reference,  inasmuch  as  it  has  recently  received  the 
attention  of  Rignoux  and  Fournier  for  their  pro- 
posed television  apparatus.  It  is  well  known  that 


POLARISING    RECEIVER  17 

if  ju,  be  the  refractive  index  of  a  substance,  and  $ 
the  angle  of  polarisation  for  that  substance,  the 
relation  holds  good. 

fji  =  tan  (/>. 

If  a  liquid  substance  contained  in  a  tube  BC 
(Fig.  4)  be  subjected  to  a  field  produced  by  a  coil 
through  which  current  is  passing,  its  refractive 
index  will  be  changed ;  hence  </>  will  be  changed 
also.  If  rays  of  monochromatic  light  from  a 
lamp  L  pass  through  one  nichol  prism  NI,  then 


<D 


FIG.  4. 

through  the  tube  BC  of  liquid  (carbon  disulphide), 
afterwards  passing  through  the  analysing  prism  N2 
and  thence  to  a  photographic  film  attached  to  a 
receiving  drum  D,  the  nichols  being  set  at  the  polar- 
ising angle,  no  light  would  reach  the  film  unless  a 
current  passed  through  the  coil  round  BC.  The 
terminals  of  such  a  coil  would  be  connected  to  the 
line  AA,  either  directly  or  through  a  relay,  and 
hence  the  film  on  D  would  record  the  impulses  sent 
through  the  coil.  The  sensitiveness  of  such  an 
apparatus  would  be  very  small  unless  a  relay  were 
employed,  and  this  would  at  once  put  a  limit  on 
the  speed  of  working,  which  wouid  seriously 
hamper  its  utility. 

P.T.  c 


18  PHOTO-TELEGRAPHY 

The  commercial  utility  of  photo -telegraphy  only 
commenced  after  the  adoption  of  Professor  Korn's 
instruments  by  the  Daily  Mirror.  Although  his 
selenium  machines  were  installed  in  Berlin  and 
Paris  at  the  same  time,  the  Daily  Mirror  in 
London  may  be  said  to  be  the  only  journal  that 
has  utilised  them,  or  any  subsequent  machine, 
in  -a  really  commercial  way.  Two  of  Korn's 
selenium  machines  were  installed  in  Stockholm 
and  Copenhagen  in  1908,  and  some  trans- 
missions have  been  made  by  the  newspapers  which 
took  up  his  system,  but  ever  since  their  instal- 
lation of  the  selenium  instrument  in  November, 
1907,  the  Daily  Mirror  has  systematically  carried 
out  transmissions  and  has  persistently  endeavoured 
to  develop  tHe  really  practical  side.  The  large 
amount  of  experimental  work  that  I  have  carried 
out  has  been  done  entirely  for  the  Daily  Mirror, 
and  the  present  state  of  efficiency  of  this  new 
science  is  very  largely  due  to  the  substantial  help 
they  have  given  to  it. 

This  chapter  has  been  written  from  a  more  or  less 
historical  standpoint,  and  it  may  therefore  be  said 
that  the  commercial  or  practical  history  commenced 
in  1907  with  the  use  of  Korn's  selenium  machines. 
The  progress  that  has  been  made  during  the  last 
two  and  a -half  years  has  been  very  considerable, 
and  has  been  almost  entirely  due  to  paying  the 
closest  attention  to  small  details.  The  mechanical 


FUTURE    PROSPECTS  ig 

parts  of  the  various  instruments  have  been  made 
with  greater  precision,  the  physical  theory  of  the 
selenium  cell  has  been  exhaustively  worked  out  by 
Korn,  who  has  also  made  a  great  deal  of  progress 
in  determining  the  best  form  of  string  for  the 
galvanometers  used  in  photographic  receivers.  M. 
Chatenet,  of  L' Illustration,  Paris,  has  done  much 
valuable  work  in  connection  with  the  preparation 
of  the  line  photographs  for  transmission,  the 
importance  of  which  will  be  seen  later. 
•  History  does  not  dip  into  the  future,  fortunately 
for  the  historian,  but  it  is  quite  clear  by  now  that 
the  telegraphy  of  photographs  has  a  commercial 
value,  and  that  this  value  will  rapidly  increase  with 
the  demands  for  pictures  made  on  modern  journa- 
lism. What  other  uses  it  will  be  put  to  remain  to 
be  seen,  but  there  are  many  possibilities.  As 
regards  distance,  where  the  cable  renders  trans- 
mission too  slow,  "wireless"  may  solve  the 
problem,  but  that  also  remains  to  be  seen. 

Before  closing  this  chapter,  I  should  like  to  refer 
once  more  to  Mr.  Gamble's  article  in  Penrose's  Pic- 
torial Annual,  which  it  is  interesting  to  recall  to- 
day, since  his  predictions  have  been  so  well  ful- 
filled. 

"  But  suppose,"  he  says,  speaking  of  illustrated 
journalism,  "  it  were  possible  to  transmit  the  picture 
over  the  wires  with  the  same  facility  as  we  now 
transmit  the  words,  and  suppose  that  the  same 

c  2 


20  PHOTO-TELEGRAPHY 

electric  current  rendered  a  transcript  of  the  picture 
in  a  form  suited  for  immediately  using  or  convert- 
ing into  a  printing  surface,  what  a  revolution  it 
would  effect  in  the  methods  of  giving  news  to  the 
public,  ...  of  whose  craving  for  illustrations 
editors  and  publishers  are  fully  conscious.  '  Quite 
so,'  says  the  practical  editor,  l  but  will  such  a  thing 
ever  be  possible  ?  I  doubt  it/ 

"  Well,  just  to  call  to  mind  what  electricity  has 
already  given  us  besides  telegraphy.  By  means  of 
this  wonderfully  potent  power  we  transmit  sound, 
light,  heat,  and  motive  energy.  Its  latest  and 
perhaps  most  marvellous  development  is  the  utilisa- 
tion of  the  so-called  *  X-rays  '  to  enable  us  to  probe 
the  mysteries  of  our  anatomy  and  search  for  things 
hidden  from  mortal  eye.  Surely  it  is  but  a  little 
step  to  annihilate  the  limitations  of  human  vision 
and  provide  us  with  a  means  of  seeing  things  from 
afar.  Undoubtedly  this  will  be  the  next  wonder 
that  electricity  has  in  store  for  us." 

Then,  after  describing  Bain's  chemical  tele- 
graph, in  which  at  the  transmitting  station  a  metal 
brush  passed  over  large  metal  type  letters  and 
closed  a  circuit  which  chemically  reproduced  the 
letters  at  the  receiving  end,  he  says  : 

"  I  mention  the  foregoing  chemical  process, 
because  I  think  it  will  suggest  to  photographic 
experimentalists  a  likely  method  of  transmitting 
pictorial  records.  For  the  letters  of  Bain's  instru- 


SOME'  PREDICTIONS  21 

ment  substitute  a  half-tone  enamel  print  on  copper 
showing  alternate  bare  and  covered  parts,  and 
the  point  then  is  to  find  a  sufficiently  sensitive 
transmitter." 

The  receiver  is  the  part  that  remained  to  be  made 
sufficiently  sensitive,  and  I  cannot  help  thinking  the 
word  "  transmitter  "  was  used  for  "  receiver  "  by 
a  slip.  How  this  sensitiveness  has  been  obtained 
will  be  explained  in  the  chapter  dealing  with  the 
telectrograph. 


\ 


CHAPTER   II. 

PROFESSOR    KORN'S    SELENIUM    PROCESS— EARLY 
WORK   WITH    HIS    ORIGINAL   RECEIVER— THE 
STRING    GALVANOMETER  —  SYNCHRONISM  - 
FIRST    EXPERIMENTS— THE    EARLY    HISTORY 
OF   COMMERCIAL    PHOTO -TELEGRAPHY. 

THE  metal  selenium  is,  in  its  crystalline  state, 
very  sensitive  to  light.  It  has  been  utilised  in 
many  instances  of  light  telephony,  from  which  it  is 

obvious  that  it  is  sen- 
sible of  extremely  rapid 
changes  in  the  illumi- 
nation. 

The    selenium     cell, 
FIG.  5.  so-called,      takes     the 

form  shown  in  Fig.  5  ;  on  a  thin  rectangular  slab  of 
slate,  steatite,  or  some  other  suitable  material,  two 
coils  of  platinum  wire  are  wound,  one  coil  being 
wound  "  inside  "  the  other,  so  that  no  turn  touches 
another  turn  ;  thus,  in  the  figure,  turns  i,  3,  5,  7, 

9  ...  belong  to  one  coil,  while  turns  2,  4,  6,  8, 

10  .    .    .  belong  to  the  other.      We  now  fill  in  the 
spaces  between  the  turns  with  selenium,  so  that  if 
the  resistance  between  turns   I  and  2  were  R,  and 
there  were  n  turns  in  each  of  the  coils,  the    total 


THE    SELENIUM    CELL  23 


resistance  of  the  "  cell  "  would  be  approximately 
TD 
-,  assuming   the  number  of  turns   very  great   and 

their  distance  apart  equal.      The  dimensions  of  the 


FIG.  6. 

cells  made  by  Giltay,  of  Delft;  Holland,  are  about 
6-3  x  2*8  cm.,  and  their  resistance  varies  between 
very  wide  limits  ;  thus  one  may  have  a  cell  whose 
resistance  is  only  20,000  ohms,  or  one  of 
R  =  250,000  11.  It  seems  to  be  a  general  rule  that 
the  greater  the  resistance  of  the  cell  the  smaller  its 
inertia,  but  it  is  by  no  means  always  the  case. 

The  selenium  has  to  be  kept  at  a  definite  high 
temperature  until  it  assumes  the  crystalline,  slate - 
coloured  form,  when  it  becomes  electrically  con- 
ductive and  sensitive  to  light.  The  light  is  appa- 
rently absorbed  and  made  to  do  wo»k  in  lessening 
the  resistance ;  the  physical  change  is  not  relaxed — 


PHOTO-TELEGRAPHY 


the  original  state  not  restored — immediately  the 
action  of  the  light  is  discontinued  ;  the  return  to 
normal  condition  is  thus  not  instantaneous;  there  is  a 
lag,  whilst  over-illumination  and  excessive  illumina- 
tion may  cause  some  long-sustained  effect  which  has 
been  conveniently  termed  fatigue.  In  Fig.  6  is  seen 
an  actual  photograph  of  a  selenium  cell. 


SE 


FIG.  7. 
The  difficulties  caused  by  these  characteristics  of 

4^ 

the  selenium  cells  will  be  readily  understood  when 
we  see  how  the  cells  are  employed  by  Korn  in  his 
system.  I  shall  therefore  describe  the  sending 
instrument  in  its  simplest  form,  after  which  we  can 
come  back  again  to  physical  considerations. 

The  principal  portion  of  the  sending  apparatus 
is  shown  in  Fig.  7.  Here  the  light  from  a  Nernst 
lamp  N  is  concentrated  by  the  necessary  lens  system 


KORN'S   TRANSMITTER  25 

on  to  the  glass  cylinder  CO',  so  that  the  rays  cross 
at  the  point  A  where  the  pencil  meets  the  first 
surface  of  the  cylinder.  A  transparent  photograph 
printed  on  a  celluloid  or  gelatine  film  is  wrapped 
round  the  cylinder,  so  that  at  A  the  light  passes 
through  one  small  point  of  it  ;  it  travels  thence 
into  the  45°  prism  P,  by  which  it  is  reflected 
upwards  upon  a  selenium  cell  SE.  The  glass 
cylinder  is  attached  to  a  shaft  with  a  screw  thread, 
which  turns  in  a  fixed  threaded  collar  T,  so  that 
when  revolved  by  a  motor  it  rises  and  turns  spirally. 
It  is  thus  seen  that  the  spot  of  light  at  A  in  effect 
traces  a  spiral  path  over  practically  the  whole 
photograph  in  due  course.  The  intensity  of  the 
light  at  any  instant  depends  on  the  density  of  the 
photographic  film  in  the  portion  traversed  at  that 
instant,  so  that  the  light  falling  upon  the  selenium 
cell  is  always  varying  in  accordance  with  the  density 
of  the  photograph. 

The  "  point  "  embraced  by  the  light  pencil  at  A 
is  in  reality  about  3X2  mm.  in  area,  hence  no 
small  details  can  be  transmitted  as  several  would 
be  embraced  at  once  by  the  beam.  This  is  the 
reason  why  only  portraits  or  very  simple  subjects 
could  be  transmitted  by  the  selenium  machines.* 

*  More  complicated  pictures  have  been  transmitted  by 
Korn's  selenium  machine  by  enlarging  up  the  subject  and 
dividing  it  into  three  or  four  parts,  telegraphing  each  separ- 
ately and  then  joining  up  the  telegraphed  components. 


26  PHOTO-TELEGRAPHY 

The  size  of  the  glass  cylinders  used  is  13  cm. 
length  by  7  cm.  diameter,  so  the  picture  transmitted 
is  22  X  13  cm.  The  pitch  of  the  thread  on  the 
axle  is  i  mm.,  so  that  the  cylinder  turns  130  times 
during  a  complete  transmission  ;  it  revolves  once  in 
5  seconds,  hence  the  time  of  transmission  is  just 
over  i  i  minutes.  Arrangements  were  provided  in 
some  of  the  machines  to  double  the  pitch  of  the 
axle  thread,  so  that  a  photograph  could  be  tele- 
graphed in  under  6  minutes.  This,  of  course, 
meant  a  corresponding  sacrifice  of  detail. 

We  must  now  return  to  the  selenium  cell  and  see 
how  its  slowness  to  respond  to  the  variations  in 
illumination  cast  upon  it  from  the  prism  have  been 
largely  overcome  by  the  ingenious  system  of  "  com- 
pensation "  worked  out  and  patented  by  Professor 
Korn  prior  to  1907.  If  a  certain  amount  of  light 
be  falling  upon  the  cell,  so  that  its  inertia  be  over- 
come, and  its  resistance  be  n,  then  any  increment, 
61  in  the  illumination  will  give  a  decrement  in  the 
resistance,  in  a  way  connecting  the  reciprocals  of 
the  resistances  r\  and  r2  as  follows  :— 

-  =  —  +  a5I, 
r*       ri  n 

or  if  the  increase  in  illumination  be  used  for  only  a 
short  time  /, 


and  /(O  converges   to  i  where  t   =   oc  •     F(/)  is  a 


SELENIUM  27 

function  of  the  time,  and  a  is  (in  both  cases)  a 
constant  depending  on  the  selenium  cell  and  its 
characteristics ;  a  can,  in  fact,  be  termed  the 
"  sensitiveness  "  of  the  cell. 

Professor  Korn  has  shown  that  where  /3  and  ;;/ 
are  inertia  constants  of  the  selenium  cell  the  change 
in  resistance  y  can  be  obtained  for  an  increase 
in  illumination  51  from  an  equation  of  the  form 

current  =  y  =  abl.e  ~  & 
where  O  <  ;;/  <  oc  ;    /3  is  the  inertia   constant  and 


FIG.  8. 

m  the  exponential  inertia ;  for  photo-telegraphic 
work  m  should  be  as  small  as  possible,  and  this  is 
obtained  best  by  using  platinum  wire  in  the 
preparation  of  the  cell  and  very  pure  selenium  ; 
m  can  be  made  as  low  as  f . 

The  relation  between^  time  and  current,  shown 
as  an  inertia  curve,  is  seen  in  Fig.  8.  In  the 
figure  we  see  the  effect  of  suddenly  illuminat- 
ing the  cell  for  a  time  which,  expressed  as  the 
abscissa,  goes  as  far  as  the  vertical  dotted  line  ; 
after  the  time  t  the  illumination  is  cut  off,  but  the 
resistance,  instead  of  increasing  again  to  normal 
instantly,  takes  a  considerable  time  as  indicated  ; 


28 


PHOTO-TELEGRAPHY 


there  is  considerable  lag,  and  it  may  actually  take 
some  seconds  before  the  resistance  becomes  the 
normal  for  no  illumination. 

Now  let  us  see  what  this  means  in  actual  photo- 
telegraphy. It  has  been  seen  that  the  transparent 
photograph  revolves  in  cylindrical  form,  so  that 
different  consecutive  parts  of  it  intercept  the  light 
beam  which,  after  reflexion  in  the  prism,  falls  on 
the  cell.  Suppose  a  bright  part  in  the  photograph 


Y 


O          I  ( ( icrmn  u.f t  071 

FIG.  9. 

is  adjacent  to  a  very  dark  part,  the  light  falling  on 
the  cell  is  great  at  the  moment  the  bright  part  inter- 
cepts the  light,  and  is  very  small  immediately  after- 
wards when  the  dark  part  takes  its  place.  The 
current  passed  through  the  cell  should  increase  with 
the  bright  part  and  instantly  fall  again  when  the 
dark  part  comes  ;  instead,  the  lag  in  the  cell  inter- 
venes, and  it  only  half  falls,  and  thus  interferes 
fundamentally  in  the  process. 

Various  means  have  been  tried  to  counteract  the 


COMPENSATION    METHOD 


29 


inertia,  and  to  my  mind  the  most  successful  is  the 
method  Korn  has  suggested  of  keeping  the  cell 
always  sufficiently  illuminated  to  overcome  it. 
Thus  suppose  we  represent  the  effect  of  light  on 
resistance  by  a  curve  of  the  form  shown  in  Fig.  9, 
the  point  P  gives  us  the  place  on  the  curve  after 


Receiving 
Galvanometer 


-/v 
FIG.  10. 

which  for  every  increment  of  light  6L  the  decrease 
in  resistance  in  a  small  time  t  is  dbR.  If  suffi- 
cient light  OL  be  allowed  always  to  fall  on  the  cell 
so  that  the  inertia  YP  is  overcome.,  the  effect  of 
any  additional  light  will  be  very  rapid.  The  com- 
pensation method  of  Korn  gives  further  a  much 
brisker  action,  and  the  scheme  is  seen  in  Fig.  10. 
Here  the  light  which  has  traversed  the  revolving 
photograph  falls  on  the  selenium  cell  S^i.  This  cell 


30  PHOTO-TELEGRAPHY 

is  placed  as  one  arm  of  a  Wheatstone  bridge, 
a  second  cell  S^2  being  placed  on  the  opposite 
arm.  W  is  a  regulating  resistance,  and  BI  and 
B2  two  batteries  of  about  100  volts,  BI  being 
provided  with  a  compensating  variable  resistance 
W2.  The  galvanometer  is  of  the  "string"  form, 
i.e.,  two  fine  wires  XY  move  laterally  in  the  field 
of  a  powerful  electromagnet,  whose  pole  pieces  MM 
are  tunnelled  with  a  hole.  A  small  piece  of 


Tim  e 


FIG.  n. 


77,™ 

FIG.  12.    . 

aluminium  or  magnesium  foil  is  stuck  to  the  wires 
in  the  centre,  and  this  shutter  just  cuts  off  the 
light  which  would  pass  from  a  Nernst  lamp  N 
through  the  poles.  If  current  passes  through 
the  wires  they  are  laterally  displaced,  and 
the  beam  of  light  can  then  reach  the  second 
selenium  cell  S^2.  As  the  current  transmitted  to 
the  receiving  station  passes  there  into  a  precisely 
similar  galvanometer,  the  circuit  is  closed. 

Now  let  us  see  what  happens  when  a  bright  part 


COMPENSATION  31 

in  the  photograph  causes  light  to  be  cast  on  the  cell 
S^i.  The  equilibrium  of  the  bridge  is  at  once  upset, 
current  therefore  passes  through  XY,  the  shutter 
is  displaced,  and  light  falls,  a  fraction  of  a  second 
later,  on  to  S^-  We  can  represent  the  effect  for  an 
illumination  I  by  the  two  curves  below  (Fig.  11) 
on  opposite  sides  of  the  time  axis.  Add  the  two 
ordinates  and  you  get  the  "  dead  beat  "  curve  shown 
in  Fig.  12.  The  effect  is  almost  instantaneous,  and 
when  the  illumination  ceases  the  current  drops  at 
once  to  zero.  This  effect  can  only  be  obtained, 


77  me 

FIG.  13. 

needless  to  say,  when  the  two  cells  are  well 
matched  ;  it  is  easy  to  have  over  -compensation,  as 
shown  in  Fig.  13,  where  the  current  is  brought 
below  zero,  and  time  is  thus  lost  in  regaining  a 
normal  condition. 

It  is  not  difficult  to  show  that  for  good  compensa- 
tion, assuming  the  equations  of  the  two  cells  be 


(ii)  ^  =  03*!.*  -*"' 
we  must  have  the  condition  fulfilled 


At 


32  PHOTO-TELEGRAPHY 

and  that  for  this  we  must  have 

ai  /3t  =  a2  /32. 

Both  cells  should  have  m  as  nearly  equal  as  pos- 
sible and  very  small — the  principal  cell  S^i  should 
have  great  sensitiveness  and  small  inertia  ;  the  com- 
pensating cell  Stf2  should  have  proportionately  small 
sensitiveness  and  large  inertia,  so  that  we  can  fulfil 
approximately  the  condition 

d!  /3i  =  a2  /32. 

A  rather  interesting  point  is  raised  by  the  fact 
that,  according  to  Ruhmer,  it  is  possible  to  sensitise 
a  selenium  cell  for  a  narrow  region  of  the  spectrum. 
He  had  utilised  cells  of  different  colour  sensitive- 
ness with  a  view  to  duplex  wireless  telephony,  but 
it  occurred  to  the  author  that  possibly  by  colour 
sensitising  a  cell  and  using  light  only  of  the  colour 
for  the  particular  illumination  the  inertia  might  be 
less,  and  possibly  the  sensitiveness  higher  ;  with  a 
cell  of  "  dark  resistance  "  /•,  the  maximum  useful 

v 
amount  of  illumination  only  lowers  this  to  perhaps  — 

Y 

or  -,  though  one  can  obtain  cells  with  a  very  large  a, 

resistance  when  dark 

so  that  the  ratio  — r—          — =- ^ = — 3  is  as  much 

resistance  when  illumined 

as  4  :  i  or  5  :  i.  Thus  a  cell  of  resistance  250,000 
ohms  will  sometimes  become  reduced  in  resistance 
to  about  60,000  when  illuminated  with  a  ^candle- 
power  lamp  held  3  inches  away  from  it.  The 


THE    STRING    GALVANOMETER         33 


maximum  sensitiveness  is  towards  the  yellow- 
orange  portion  of  the  spectrum,  but  the  inertia 
appears  to  be  unaffected  by  the  wave-length, 
though  Korn  has  patented  the  method  of  using  a 
selected  colour.  Several  experiments  were  made 
in  England  screening  the  light  with  colour  filters, 
so  that  light  of  known  wave-lengths 
was  used  for  illuminating  the  cells. 
The  results  of  a  series  of  measure- 
ments showed  that  there  was  no 
advantage,  the  lag  being  the  same 
as  when  ordinary  Nernst  light  was 
employed. 

Before  describing  the  actual  re- 
ceiving apparatus  of  Korn's  selen- 
ium machines  it  will  be  of  interest 
to  see  the  construction  of  the  gal- 
vanometer, to  which  he  has  given 
so  much  attention,  and  which  is  of 
extreme  sensitiveness,  especially 
when  of  the  modified  form  as  used  in  his  later ' '  telauto- 
graph "  (see  next  chapter).  The  field  magnets  are 
powerful,  and  the  pole  pieces  measure  about 
5  X  ii  X  4  cm.  These  converge  nearly  to  points 
in  the  centres,  as  shown  in  Fig.  14.  Thus  they 
nearly  touch  at  AB,  only  sufficient  room  being  left 
for  two  fine  silver  wires  to  move  freely  between 
them.  The  hole  through  the  poles  is* shown  in  the 
diagram,  and  a  sliding  tube  T  fitted  with  a  small 

P.T.  D 


34 


PHOTO-TELEGRAPHY 


i  K 


i  Adjusting 

Screw 
M 


short  focus  lens  is  provided  in  the  hole  nearest  the 
receiving  box.  The  shadow  of  a  magnesium 
shutter  (described  later)  attached  to  the  wires  can 
be  sharply  focussed  upon  a  diaphragm  by  sliding 
the  tube  T  to  the  correct  position. 

A  metal  collar  (indicated  by  the 
dotted  circle)  is  fixed  above  the 
pole-pieces  into  which  the  moving 
part  of  the  galvanometer  is  fitted  ; 
this  part  is  shown  separately  in 
Fig.  15.  The  outside  portion  of 
this  (MN)  is  a  cylindrical  tube 
which  fits  into  the  collar.  A  sliding 
piece  S  is  free  to  move  up  and 
down  inside  the  tube,  and  is  fitted 
with  a  screw  thread,  over  which  a 
graduated  adjusting  nut  is  placed. 
By  turning  this  regulating  screw,  S 
is  moved  up  or  down  and  the 
tension  on  the  wires  varied.  The 
wires,  about  T^oo^h  ^ncn  thick,  are 
attached  to  two  very  fine  springs  (of 


FIG.  15. 


the  same  material)  fitted  to  S.  The  small  shutter  F, 
about  2  X  1*5  mm.  in  area,  and  as  thin  as  possible,  is 
gummed  to  the  wires  so  that  it  comes  on  the  optic 
axis  when  the  piece  is  fitted  into  the  magnet  collar. 
The  sliding  portion  S  is  insulated  from  the  brass 
tube,  but  is  connected  with  a  contact  K.  This  con- 
tact and  another  metal  button  C  fit  against  two 


THE   STRING    GALVANOMETER         35 

corresponding  contacts  in  the  field  magnet  collar, 
which  are  in  turn  connected  with  the  sliding 
contacts  of  the  resistances  already  described. 

The  weight  of  the  "  moving  part  "  of  the  galva- 
nometer is  almost  negligible,  its  moment  of  inertia 
extremely  small,  and  with  the  length  of  wires  used 
a  period  of  swing  as  small  as  y^Jo^h  of  a  second  can 
be  obtained.  The  current  flows  in  at  C  and 
traverses  the  fine  wires  upwards  from  bottom  to 
top,  leaving  them  at  K.  The  field  due  to  each  is 
thus  similar,  hence  their  displacement  is  lateral,  and 
is  approximately  equal  to 

C  (_ \  ><  constant  of  galvanometer. 

\?i        r2/ 

We  may  regard  the  wires  as  elastic  substances 
stretched  across  the  apparatus,  where  the  dis- 
placement D  can  be  represented  by  f(e),  or  some 
function  of  the  elasticity  ;  the  wires  can  be  set  in 
vibration,  and  if  one  impulse  be  given  by  passing 
a  sudden  short  period  current  through  the  wires, 
when  displaced  thereby  through  a  distance  D  they 
have  sufficient  potential  energy  to  cause  them  to 
swing  back  past  the  position  of  rest  through  a 
distance  slightly  smaller  than  D  in  the  same 
manner  as  a  pendulum.  This  is  clearly  shown  by 
the  photographic  records  (p.  no)  obtained  of  the 
movements  of  the  shutter  F  recorded  under  various 
circumstances  on  a  moving  photographic  film. 
This  period  can  be  made  shorter  by  using  shorter 

D  2 


36  PHOTO-TELEGRAPHY 

"  strings  "  or  wires.,  but  as  there  is  a  practical 
limit  to  their  fineness,  we  must  make  the  factor  e 
increase  by  the  strings  becoming  shorter  ;  hence  the 
current  necessary  to  displace  them  an  equal  amount 
becomes  greater,  and  where  selenium  is  used  its 
resistance  is  so  high  that  a  limit  is  immediately 
set  to  the  length  of  strings  practicable.  The 
magnetic  field  may  of  course  be  increased  when  the 
galvanometer  constant  K  in  the  expression 

D  =  CK  (— )  becomes  greater.    The  Einthoven 

\r\       r*J 

galvanometer,  of  which  Korn's  apparatus  is  a 
special  form,  is  often  provided  with  a  far  greater 
field  than  he  employs. 

Once  in  each  revolution  of  the  receiving  drum 
there  is  a  distinct  kick  in  the  galvanometer,  as  for 
the  synchronising  of  the  sending  and  receiving 
apparatus  it  is  necessary,  as  will  be  seen  later,  to 
cut  the  current  out  of  the  galvanometer  circuit  and 
switch  it  into  the  synchronising  gear.  This  kick, 
due  to  a  capacity  discharge  front  the  line,  was  to 
some  extent  overcome  by  Korn  by  shunting  a  small 
resistance  across  the  galvanometer  at  the  terminals 
K,  C.  To  facilitate  its  regulation  I  replaced  this 
fixed  resistance  by  a  regulating  shunt  resistance  of 
o  to  50  ohms,  but  it  was  ultimately  found  that  the 
kick  could  be  best  avoided  by  very  careful  adjust- 
ment of  the  position  of  the  fleeting  contact  through 
which  the  synchronising  current  passed. 


KORN'S   SELENIUM    RECEIVER 


37 


The  shadow  of  the  galvanometer  foil  is  cast 
upon  a  triangular  aperture  in  a  diaphragm  E 
(Fig.  1 6),  being  magnified  up  a  good  many 
times  by  the  lens  T  which  is  fitted  into  one  pole 
of  the  electro -magnet.  This  shadow  prevents 
the  light  from  the  lamp  N  reaching  the  small 
lens  O  which  concentrates  a  real  image  of  the 
aperture  (when  illuminated)  upon  the  photo- 
graphic film  ;  this  revolves  on  the  drum  D,  the 


*o 


FIG.  16. 

drum  being  fitted  into  a  small  light-tight  wooden 
box.  Now  if  the  shutter  is  displaced,  the  shadow 
moves  to  one  side,  and  light  immediately  passes 
through  the  aperture  at  E  and  exposes  the  film. 
The  more  the  shadow  moves  towards  the  base  of 
the  triangular  hole,  the  greater  is  the  light  which 
reaches  the  film  ;  by  using  a  triangular  instead  of  a 
square  hole  the  effect  of  movement  of  the  shutter 
on  the  light  transmitted  to  the  film  is  obviously 
amplified,  and  this  amplification*  is  necessary 
because  the  ratio  of  illumination  to  resistance  of 


38  PHOTO-TELEGRAPHY 

the  selenium  in  the  sending  apparatus  is  not  con- 
stant, but  decreases  as  the  illumination  increases. 
The  angle  at  the  apex  of  the  triangle  has  some- 


FIG.  17. — Photograph  of  galvanometer  as  used 
by  Prof.  Korn. 

times  to  be  altered  to  suit  a  particular  cell,  but  is 
usually  about  50°  to  60°.  The  shutter,  and  hence 
the  shadow  on  E,  is  constantly  moving  more  or  less 
towards  the  base  of  the  triangle  according  to  the 
strength  of  the  current  and  therefore  to  the  density 


SYNCHRONISING 


39 


of  the  photograph  being  transmitted.  The  area 
of  the  picture  received  is  one  quarter  that  of  the 
film  used  in  transmission. 

The  method  of  synchronising  the  sending  and 
receiving  cylinders  now  requires  explanation.  A 
small  error  in  synchronisation  will  cause  distortion 
of  the  picture  received,  and  great  care  is  required 


Line 


To  Galvanometer 


To  Battery 


FlG.   18. 

to  ensure  its  accurate  adjustment.  In  Fig.  18 
let  us  suppose  that  C  is  the  cylinder  of  the  trans- 
mitting apparatus,  and  D  the  receiving  drum. 
There  is  a  projecting  pin  on  the  bottom  of  the 
transmitting  cylinder  which  once  in  each  revolu- 
tion strikes  against  a  contact  spring,  throwing 
it  away  from  contact  with  P  and  into  contact 
with  Q.  When  the  spring  is  in*  contact  with 
p_during  practically  the  whole  revolution— the 


40  PHOTO-TELEGRAPHY 

selenium  circuit  flows  through  the  line  to  the 
receiver.  When  it  is  displaced  and  connects  with 
Q,  the  current  from  the  battery  has  merely  to  pass 
through  a  small  fixed  resistance,  about  one -tenth 
that  of  the  selenium,  so  that  the  current  is  some  ten 
times  as  great.  As  soon  as  the  cylinder  has  turned 
a  little  more,,  the  spring  returns  into  contact  with 
P  again. 

Now  at  the  receiving  machine  we  have  a  similar 
pin  which  throws  over  a  spring  N  from  contact  with 
R  into  contact  with  S.  Whereas  R  leads  to  the 
galvanometer,  S  leads  to  one  coil  of  a  relay  as 
shown,  the  other  coil  of  the  relay  being  con- 
nected with  the  other  unit  of  the  line,  together  with 
the  other  end  of  the  galvanometer. 

What  happens  then  is  that  every  time  the  pin  on 
the  sending  cylinder  throws  the  spring  against 
the  contact  Q,  a  strong  current  is  transmitted 
through  the  line.  If  at  that  instant  the  corre- 
sponding spring  N  of  the  receiver  be  also  thrown 
against  S,  the  current  received  passes  into  the 
relay  instead  of  into  the  string  galvanometer. 

By  making  the  drum  D  turn  quicker  than  the 
cylinder  C  it  will  obviously  reach  the  end  of  its 
revolution  first.  It  is  then  suddenly  stopped  by 
the  check  T,  which  strikes  against  a  movable 
steel  check  F.  When  the  slower  turning  send- 
ing cylinder  has  finished  its  revolution,  the 
strong  current  is  sent,  as  we  have  seen,  into 


SYNCHRONISING    MECHANISM 


the  relay,  exciting  the  coils  and  causing  the 
small  magnetised  armature  to  be  attracted  to- 
wards the  left  side  in  the  diagram.  The  pla- 
tinum contacts  XX  then  touch,  and  current  from 
the  local  battery  passes  through  the  magnet  Z. 
This  attracts  the  armature  H,  so  that  the  check  turns 
about  the  fulcrum  F  into  a  position  such  that  T 
is  free  to  move  and  the  drum  consequently  again 
starts  running. 

The  motive  me- 
chanism driving  the 
drum  cannot  of 
course  stop  and 
start  abruptly  at  the 
end  of  each  revolu- 
tion, a  friction 

clutch    is    therefore 

u 
provided,  as  shown 

in  the  next  diagram  (Fig.  19).  The  shaft  is 
cut  through  and  two  parallel  faces  FF  fitted, 
springs  SS  being  attached  to  the  lower  one  which 
grip  the  upper  one.  When  the  motion  of  the 
cylinder  is  checked,  the  two  faces  turn  one  against 
the  other.  The  springs  are  fixed  to  a  collar  C 
which  can  be  screwed  over  the  threaded  shaft, 
K  being  a  lock  nut.  The  tension  of  the  friction 
clutch  can  thus  be  regulated. 

The  transmitting  cylinder  is,  as  'already  stated, 
revolved  at  about  the  rate  of  one  revolution  in  five 


% 

m 

V 

% 

1 

% 

^ 

% 

H 

F 

y 
v. 

Fm 

\ 

( 

I 

1 

n 

FlG- 


42  PHOTO-TELEGRAPHY 

seconds,  or  in  reality  at  about  T9o9oths  of  this  speed  ;  as 
the  receiving  drum  must  revolve  quicker,  in  order 
to  be  stopped  and  then  restarted  by  the  synchronism 
signal  of  the  transmitter  after  each  complete  revolu- 
tion, it  is  run  at  about  xuitns  °f  the  speed.  There  is 
thus  a  difference  of  2  per  cent,  in  the  rates  of  the 
two,  which  means  an  unavoidable  elongation  of  the 
received  image. 

The  regulation  of  the  motors  is  carried  out  by 
means  of  regulating  resistances  and  frequency 
metres.  The  motor  acts  to  a  small  extent  as  a 
dynamo,  as  two  sections  of  the  armature  are  con- 
nected to  slip  rings  with  brushes  fitted,  so  that  an 
alternating  current  is  derived  from  them.  This 
alternating  current  is  supplied  to  an  electro- 
magnet, whose  polarity  at  one  pole -piece  therefore 
changes  twice  in  each  revolution  of  the  armature. 
A  row  of  tuned  steel  magnetised  springs  is  fixed 
in  front  of  the  pole -piece,  fixed  at  the  base  and  free 
to  vibrate  vertically.  These  springs  are  thus 
attracted  and  repulsed  at  each  revolution  of  the 
motor,  and  if  a  certain  spring  among  them  be  cut  to 
such  a  length  that  its  period  is  equal  to  the  period  of 
the  alternating  current,  it  will  vibrate  very  freely, 
while  other  springs  not  in  tune  will  not  vibrate  at  all . 

Now  several  such  springs,  so  cut  that  their 
periods  range  from  97  per  second  to  103  per 
second,  are  fixed  at  their  lower  ends  in  front  of  the 
pole -piece  pf  the  electro -magnet.  By  means  of  the 


THE    FREQUENCY    METER  43 

regulating  switch  of  the  motor  —  an  ordinary 
variable  resistance  in  series  with  the  field  magnets 
— the  motor  can  be  speeded  up  until,  say,  the  spring 
labelled  99  vibrates  freely.  The  motor  is  then 
revolving  %9  times  a  second,  or  just  under  3,000 


FIG.  20. 

times  per  minute.  This  is  the  condition  for  the 
motor  of  the  sending  apparatus.  The  face  of  the 
meter  is  shown  in  Fig.  20. 

Similarly  at  the  receiving  station  the  operator 
runs  his  motor  at  just  over  3,000  revolutions  per 
minute.  Each  motor  is  geared  doWh  with  a  worm 
drive  in  oil,  which  has  to  work  very  sweetly  in  order 


44 


PHOTO-TELEGRAPHY 


to  prevent  vibration.  In  many  later  models  of 
photo  -  telegraphic  apparatus  the  motors  are 
mounted  on  separate  stands  and  connected  to  the 
driving  gear  by  flexible  shafting. 

The  relay  used  by  Professor  Korn  for  utilising 
the    synchronising    current  to  close  the  magnetic 


FIG.  21. 

check  release  circuit  is  a  Siemens  &  Halske  polar- 
ised relay.  A  polarised  relay  is  not  necessary 
unless  it  be  sufficiently  sensitive  to  work  with 
a  current  equal  in  intensity  to  the  line  current  for 
the  galvanometer.  The  Siemens  &  Halske  relay 
can  be  rendered  more  or  less  sensitive  at  will  by 
regulating  the  distance  of  one  magnet  from  the 
armature  it  has  to  attract,  keeping  the  other 
magnet  fixed. 


THE    SWITCH-BOARD  45 

The  whole  arrangement  of  Professor  Korn's 
selenium  instruments  has  now  been  described,  and 
there  remains  only  the  description  of  the  actual 
commercial  working  to  be  given.  It  is  clear 
that  there  must  be  some  means  of  communication 
between  the  operators  of  the  sending  and  receiving 
machines .  As  a  metallic  circuit  is  necessary  owing 
to  the  weakness  of  the  current  transmitted,  tele- 
phone lines  are  employed,  and  these  must  be  quite 
isolated  and  free  from  annunciators  or  shunts.  A 
convenient  arrangement  is  made  by  which  the 
operator  can  switch  at  will  the  line  into  his  instru- 
ment or  into  the  telephone.  The  switchboard  is 
shown  in  Fig.  21 . 

There  are  two  change-over  telephone  switches 
on  the  board  as  shown.  The  change-over  contacts 
of  one  are  connected  to  two  terminals  AA,  which 
lead  to  the  receiving  machine,  denoted  by  G  for 
convenience.  One  of  these  lines  passes  first  through 
the  milliampere  metre  MA  to  indicate  the  strength 
of  the  line  current.  The  change-over  contacts  of 
the  other  switch  go  to  the  telephone  line.  It  will 
be  seen  that  when  the  switches  are  in  the  position 
shown  the  telephone  line  goes  direct  to  the  tele- 
phone T,  and  the  machine  terminals  are  in  connec- 
tion with  a  1,000  <Q  resistance  R.  When  switched 
over  towards  the  right  the  machine  is  in  connection 
with  the  telephone  line,  and  the  telephone  instru- 
ment is  out  of  circuit.  The  three  terminals  C  give 


46  PHOTO-TELEGRAPHY 

100  and  200  volts  to  the  selenium  cells  in  the 
manner  already  shown  in  the  compensation 
diagram,  while  current  is  led  from  P  to  the  motor 
and  galvanometer  magnets. 

It  is  hardly  necessary  to  say  that  accumulators 


'mm 


FIG.  22. — Prof.  Korn  at  the  telephone,  when  awaiting 
the  first  picture  from  Paris  in  1907. 

are  essential  in  order  to  ensure  smooth  running  and 
constant  current. 

Much  trouble  is  experienced  with  some  selenium 
cells,  while  others  will  last  without  any  bother  for 
many  months.  The  "  fatigue  "  often  spoken  of  is 
really  a  permanent  lag  in  the  cells;  a  definite 
physical  change  appears  gradually  to  take  place  in 


FAULTS    OF   SELENIUM 


47 


the    selenium   with   the   result   that   they   are   less 

sensitive  to  light,   and  the  ratio   of  their   "  light 

sensitiveness  "   to   "  dark  sensitiveness  "  becomes 

less.     They  are  sometimes  enclosed  in  glass  cells 

which  are   sealed  and  exhausted,  but   this   is   not 

done  in  the  case  of  Professor  Korn's  machines.   A 

cell  is  liable  sometimes  to  get  into  a  certain  state 

which    renders    the    current    "  intermittent/'    i.e., 

continuous    but   always 

variable,    the    variation 

amounting    perhaps    to 

10  or  20  per  cent.    This 

trouble  would  appear  to 

be  due  to  bad  contact 

somewhere,  but  it  is  in 

reality  a  fault  of  certain 

old    cells.      The    most 

successful     working    of 

the  selenium    machines 

was   obtained    after 

adopting  the  method  patented  in  1908  by  Professor 

Korn  for  keeping  the  cell  always  slightly  illuminated, 

so  that  the  inertia  was  overcome.     If  the  curve  given 

in  Fig.  23  represent  the  effect  of  light  of  increasing 

intensity  upon  the  current  (or  reciprocal  resistance 

of  the  cell),  then  that  portion  of   the  curve  shown 

would  be  the  best  to  use  for  photo-telegraphy,  where 

r* 
the  ratio     -  is  more  or  less  constant ;  {hat  part  of  the 


/n  this  portion 


1 1 1  u  m  ina  tio  n 

FIG.  23. 


48  PHOTO-TELEGRAPHY 

curve  to  the  left  of  the  first  vertical  line  represents  the 
amount  of  light  continually  falling  on  the  cell  before 
any  additional  illumination  from  the  photographic 
transparency  falls  upon  it.  Within  the  portion 

2\c* 
selected   -^-   is  almost  constant,  and  on  it  will  depend 

largely  the  shape  of  the  triangular  aperture  in  the 
receiving  diaphragm. 

The  first  photograph  wired  by  Korn's  new  sele- 
nium machines  was  received  from  Berlin  at  the 
office  of  the  French  illustrated  weekly  paper, 
L?  Illustration,  in  October,  1907.  It  was  a  photo- 
graph of  President  Fallieres,  and  came  through 
with  considerable  success.  The  first  night  of  the 
trials  Berlin-Paris,  Professor  Korn  and  his  wife, 
his  assistant  Herr  Will,  and  several  post  office 
officials,  and  some  of  the  leading  newspaper  men 
of  Paris,  were  present.  As  the  telephone  lines  were 
to  be  required  for  an  hour  or  two,  it  was  necessary 
to  make  the  experiments  very  late,  and  the  line  was 
promised  for  midnight.  After  some  minutes  we 
got  the  connection  with  Berlin,  but  there  was  an 
annunciator  bridged  across  it,  and  we  could  get 
practically  no  current  at  Paris.  Every  effort  was 
made  by  the  Director  of  Telephones,  and  we  all 
waited  patiently  until  after  two  o'clock  in  the  morn- 
ing, with  no  result,  and  finally  everyone  was  obliged 
to  leave,  feeling  both  tired  and  disappointed. 

On  the  next  occasion,  however,  the  picture  of 


FIRST   TRANSMISSIONS 


49 


Fallieres  was  received,  and  a  photograph  wired  to 
Berlin  from  Paris.  At  Berlin  Dr.  Glatzel  was 
in  charge,  the  instrument  being  installed  at  the 
office  of  the  Lokal  Anzeiger. 

A  few  days  later  Professor  Korn  left  for  London, 
leaving  M.  Chatenet  at 
Paris  as  operator,  and 
I  brought  the  Daily 
Mirror  instrument 
with  me  to  London. 
The  Paris  and  London 
instruments  had  been 
made  by  J.  Carpentier, 
the  well-known  scien- 
tific instrument  maker 
of  the  Maison  Rhum- 
korff. 

The  Paris-London 
photo-telegraphic  ser- 
vice was  inaugurated 
on  November  7th, 
1907,  when  Professor 
Korn  received  the  first 
photograph  from  Paris  at  the  Daily  Mirror  office. 
Every  facility  was  then  and  has  since  been  given  by  the 
officials  of  the  General  Post  Office,  and  much  courtesy 
has  been  shown  throughout  by  Major  O'Meara,  Mr.  F. 
Tandy,  and  other  of  the  chief  telephone  engineers 
of  this  country.  The  two  above  officials  were 


FIG.  24. — One  of  the  first  photo- 
graphs wired  by  Korn's  com- 
pensated selenium  machines. 


50  PHOTO-TELEGRAPHY 

present  at  the  first  Paris-London  trial,  and  attended 
the    lecture    given    by    Professor    Korn    on    that 


FIG.  25 

occasion.  The  photograph  first  wired  to  London 
was  one  of  King  Edward  VII.,  and  it  is  repro- 
duced in  Fig.  25.  The  original  was  an  exceed- 


LINES    IN    PHOTOGRAPHS  51 

ingly  good  photograph,  eminently  suited  to 
the  selenium  process,  and  it  is  a  peculiar 
fact  that,  as  far  as  an  actual  face  is  con- 
cerned, that  photograph  still  remains  the  most 
perfect  ever  transmitted,  putting  aside  the  purely 
technical  peculiarity  of  the  stripes  or  bands  of  which 
it  is  composed.  These  lines  in  the  photograph 
correspond  to  the  threads  of  the  screw  axle  ion  which 
depends  the  upward  travel  of  the  receiving  drums, 
and  they  make  an  angle  with  a  line  drawn  hori- 
zontally across  the  greatest  length  of  the  picture  of 

approximately   sin~J(-p-l.     The  lines   can   be  got 

rid  of  by  placing  the  small  lens  which  concentrates 
the  light  from  the  triangular  diaphragm  upon  the 
film  at  a  greater  distance  from  the  film,  but  the 
sharpness  of  definition  of  the  photograph  then  at 
once  suffers.  This  may  sometimes  be  all  the  better 
in  the  case  of  a  portrait  where  the  diffusion  renders 
the  result  much  more  "  photographic/'  But  the 
sharpest  definition  is  necessary  where  any  attempt  is 
made  to  telegraph  a  picture  with  any  small  detail 
in  it.  "  Small  detail  "  is  in  itself  a  limited  term, 
as  only  very  bold  and  simple  subjects  can  be  trans- 
mitted with  apparatus  of  this  size,  and  hence  its 
almost  exclusive  application  to  the  telegraphy  of 
portraits.  The  lens  above  referred  to  should  cast 
an  image  of  the  triangular  aperture  on  the  film 
which  is  almost  a  point. 

E  2 


52  PHOTO-TELEGRAPHY 

More  contrast  could  be  got  in  the  received  pic- 
tures by  placing  over  the  diaphragm  a  graduated 
glass,  made  by  exposing  a  photographic  plate  to  a 
fixed  light  some  distance  away  and  gradually 
uncovering  it,  so  that  on  development  one  end 
is  very  dense,  the  other  very  transparent,  density 
graduating  into  transparency.  By  cementing  such 
a  glass  to  the  diaphragm  so  that  at  the  apex  you 
have  a  dense  part  gradually  becoming  more  trans- 
parent as  you  approach  the  base,  the  effect  is  to  get 
far  more  light  through  as  the  shutter  uncovers  the 
triangular  hole  than  would  be  the  case  otherwise. 

About  the  time  of  the  first  trials  with  Korn's  sele- 
nium apparatus,  the  submarine  telephone  lines  link- 
ing this  country  with  France  were  rather  faulty, 
and  it  was  only  occasionally  that  we  were  able  to 
have  line  for  experimental  purposes.  The  average 
business  telephone  call  lasts  six  minutes,  and  in 
these  early  days  we  wanted  it  for  at  least  half  an 
hour ;  hence,  when  one  or  more  lines  were  "  down," 
the  pressure  on  the  others  was  so  great  that  the 
telephone  authorities  were  quite  unable  to  give  us 
the  use  of  one.  The  consequence  was  that  experi- 
ments were  few  and  far  between,  and  often  we  found 
the  line — quite  good  for  the  purposes  of  ordinary 
telephony — unsuitable  for  our  own  trials.  This 
state  of  affairs  continued  for  some  months,  but  in 
the  spring  matters  improved,  and  we  were  able  to 
make  numerous  experiments,  generally  obtaining 


EARLY    EXPERIMENTS 


53 


FIG.  26. 

the  line  for  about  half -an -hour  soon  after  eight 
o'clock.  The  results  were  affected  by  various 
factors,  the  chief  of  them  being  leakance.  Three- 
quarters  of  a  milliampere  is  about  the  minimum 


54  PHOTO-TELEGRAPHY 

current  possible  to  work  with,  and  we  frequently 
only  received  about  half.  The  optical  arrange- 
ments could,  of  course,  be  easily  modified  to  com- 
pensate for  this,  but  unless  the  tension  in  the 
galvanometer  strings  was  above  a  certain  figure, 
its  action  was  uncertain. 

Induction  from  other  lines  was  very  marked  at 
certain  times,  and  at  first  it  was  thought  that  this 
was  due  to  weather  conditions.  The  observed 
facts,  however,  showed  this  not  to  be  the  case  ; 
induction  effects  were  chiefly  due  to  line  condi- 
tions. The  two  systems  of  telegraphy,  Morse  and 
Baudot,  gave  marked  induction  effects,  and  tele- 
graphic experts  declared  they  could  actually  read 
Morse  messages  on  some  of  the  photographs. 
Induction  effects  can  be  seen  on  looking  at  the 
photograph  shown  in  Fig.  26,  where  they  cross 
the  photograph  at  regular  intervals. 

The  photographic  image,  as  will  have  been 
gathered,  consists  really  of  one  long  spiral  line  of 
varying  thickness  and  intensity,  which  becomes 
resolved  into  parallel  lines  when  the  image  is 
changed  from  its  cylindrical  form  and  laid  out  flat. 
The  thickness  of  the  line  is  increased  by  the  in- 
duction, hence  the  dots  and  dashes  are  graphically 
represented  in  the  received  photograph. 

In  the  Baudot  telegraphic  system  there  is  a 
periodic  current,  and  the  stripes  seen  are  at 
regular  intervals  across  the  picture.  These  marks 


EARLY   TROUBLES 


55 


were  at  first  presumed  to  be  due  to  some  mechanical 
trouble. 


cd 

CU 


OH 

ed 


CD 

d 

ri 

<-W 

o 
'E. 

W 


Photographs  telegraphed  from  Paris  now  became 
a  fairly  regular  feature  in  the  Daily  Mirror y  and  a 


56  PHOTO-TELEGRAPHY 

great  many  people,  among  them  some  of  our  lead- 
ing scientific  men,  began  to  watch  the  results  with 
curiosity.  Some  of  them  doubtless  wondered 
whether  the  system  would  ever  have  much  com- 
mercial utility,  and  the  limit  set  to  the  process 
owing  to  one  being  confined  to  the  transmission  of 
portraits  made  this  easily  understood.  It  was  not 
until  the  installation  of  Korn's  telautograph  (see 
next  chapter)  that  the  enormous  possibilities  of 
photo-telegraphy  became  clear. 

The  Franco -British  Exhibition  took  place  in 
1908,  opening  in  May,  and  the  selenium  machines 
were  exhibited  there  by  the  Daily  Mirror  in  a  small 
pavilion  erected  for  the  purpose.  The  drawback 
to  such  a  method  of  demonstration  was  that,  beyond 
watching  the  movement  of  the  galvanometer  shutter 
and  the  revolving  photographic  transparency,  little 
was  to  be  seen.  A  trunk  line  was  installed,  and 
photographs  were  received  from  Paris  at  the  pavi- 
lion each  evening  that  the  line  was  available.  A 
picture  of  the  King  was  transmitted  at  four  o'clock 
on  the  afternoon  when  His  Majesty  formally  opened 
the  exhibition. 

The  great  fire  which  occurred  in  September, 
1908,  and  burnt  the  Paris  telephone  exchange  to 
the  ground,  will  doubtless  be  remembered.  This 
effectually  put  a  stop  to  photo -telegraphic  experi- 
ments, and  little  more  was  done  except  to  give 
demonstrations  to  the  visitors.  As  a  general  rule 


THE    MANCHESTER    STATION          57 

the  whirring  noise  of  the  motors  excited  the 
curiosity  of  people  outside  the  little  pavilion,  and 
large  crowds  endeavoured  to  come  inside,  a  queue 
some  fifty  yards  long  occasionally  awaiting  their 
turns  outside.  The  pavilion  would  get  so  full  that 
those  farthest  away  from  the  barrier  could  see 
nothing.  On  one  such  occasion  two  elderly  ladies 
squeezed  their  way  in,  and  after  waiting  patiently 
some  ten  minutes  and  seeing  nothing  but  the  backs 
of  other  people  they  came  out  again,  and  the 
following  conversation  ensued  : — 

FIRST  LADY  :  "  How  very  wonderful  it  is  !  " 

SECOND  LADY:  "Extraordinary!     Marvellous!" 

FIRST  LADY  :  "  Did  you  see  anything  ?  " 

SECOND  LADY  :   "  No,  I  could  see  nothing.      Did  you  see 

anything  ? " 
FIRST  LADY  :  "  Nothing." 

The  demonstrations  continued  until  the  close  of 
the  exhibition,  by  which  time  they  badly  needed 
overhauling.  This  took  some  time,  and  when 
finished,  it  was  decided  to  instal  one  of  them  at 
Manchester,  in  order  to  facilitate  the  transmission 
to  London  of  north -country  pictures. 

The  instrument  was  placed  at  the  offices  of  the 
Manchester  Courier,  the  installation  being  as  follows: — 

One  80  ampere  hour  no  volt  set  of  accumulators,  with 
charging  board,  etc.,  for  the  motor,  lamp  and  magnet. 

One  2  ampere  hour  210  volt  set  of  accumulators  for  the 
selenium  cell  line  circuit. 

Trunk  Telephone  and  change-over  switches  as  described. 


58  PHOTO-TELEGRAPHY 

The  line  from  Manchester  was  shorter  and  more 
satisfactory  for  the  selenium  machine  than  the 
Paris- London  line,  and  the  results  obtained  were 
very  fair.  Photographs  were  frequently  tele- 
graphed to  Manchester  and  published  in  the  Man- 
chester Courier,  while  every  evening  some  portrait 
of  topical  interest  was  sent  from  Manchester  to 
London.  Soon  after  this  service  began,  the  Paris 
lines  were  again  available,  and  the  Paris-London 
service  was  again  continued. 

Several  experiments  were  made  with  a  view  to 
transmitting  landscapes  or  sporting  pictures  instead 
of  simple  portraits  by  dividing  the  original  picture 
into  two  or  three  parts  and  telegraphing  one  part  at 
a  time,  afterwards  joining  up  the  sections.  This 
method  is  quite  plausible  in  theory,  but  unfortu- 
nately only  worked  out  in  practice  in  the  labora- 
tory. Each  portion  takes  twelve  minutes  to 
transmit,  and  often  during  such  time  the  condi- 
tion of  the  lines  would  vary  sufficiently  to  render 
the  next  portion  quite  different  in  character. 
These  differences  could  have  been  made  good 
by  retouching,  had  the  time  available  permitted 
of  it.  But  it  must  be  remembered  that  where 
a  photograph  is  telegraphed,  it  is  usually  sent 
at  a  late  hour,  and  if  much  time  be  spent  on 
the  retouching,  it  may  be  too  late  for  publica- 
tion. 

The  public  is  very  suspicious,  and  scientific  men 


JOURNALISTIC    USES  59 

are  apt  to  ignore  or  disbelieve  things  with  which 
they  are  not  personally  intimate,  and  the  opinion, 
I  know,  prevailed  at  one  time  that  many  of  the 
telegraphed  pictures  were  greatly  retouched  or 
"  faked  "  before  they  were  printed  in  the  paper. 
Let  me  say  here,  therefore,  once  for  all,  that  tele- 
graphed pictures  have,  of  necessity,  less  retouching 
than  the  ordinary  photographs,  and  unless  they 
arrive  over  the  wire  tolerably  good  in  quality  they 
are  absolutely  useless.  The  idea  that  the  results 
were  faked  arose  from  mere  ignorance  of  the  vital 
conditions  under  which  commercial  photo -tele- 
graphy is  possible. 

The  selenium  machines  were  kept  running  at 
Manchester  and  Paris  until  Professor  Korn  had 
completed  tests  between  Berlin  and  Paris  with  his 
telautograph.  They  served  a  useful  purpose,  as 
they  inaugurated  a  new  branch  of  electrical  science 
which  is  destined  to  play  an  important  part  in 
modern  illustrated  journalism.  An  instance  of  the 
criminalistic  possibilities  of  photo-telegraphy  was 
shown  in  1908,  when  a  man  named  Hedemann, 
whose  photograph  was  telegraphed  from  Paris  to 
London  and  published  in  the  Daily  Mirror,  was 
recognised  by  someone  in  London  who  knew  him 
and  gave  important  information  to  the  police. 

Professor  Korn  is  at  present  endeavouring  to 
render  more  satisfactory  his  compensation  of  the 
lag  in  the  selenium  cell,  and  eventually  to  prepare 


60  PHOTO-TELEGRAPHY 

instruments  based  on  selenium  for  experiments 
across  the  Atlantic.  Herr  Riihmer,  whose  work  in 
connection  with  wireless  telephony  is  well  known, 
and  who  has  contributed  many  valuable  papers  on 
the  physical  properties  of  selenium,,  claims  now  to 
have  completely  overcome  inertia  in  certain  new 
cells  he  has  made.  He  is  using  selenium  cells  in 
experimental  trials  to  transmit  by  electricity  a  visual 
image  of  an  object  or  person,  but  as  his  work  con- 
cerns television  and  not  the  telegraphy  of  pictures, 
it  will  not  be  discussed  here. 


CHAPTER   III. 

THE  KORN  TELAUTOGRAPH  —  PRINCIPLES  OF 
WORKING— ADVANTAGES  OVER  SELENIUM- 
EARLY  WORK  WITH  LINE  PICTURES— EXPE- 
RIMENTS WITH  TELEPHONE  AND  TELEGRAPH 
CABLES  —  RECENT  PROGRESS  WITH  THE 
TELAUTOGRAPH. 

THE  telautograph  as  arranged  by  Professor  Korn 
is  really  a  combination  of  Caselli's  transmitter  with 
the  Einthoven  galvanometer  and  photographic 
receiver  as  used  in  the  selenium  machines.  From 
the  very  first  the  stringent  limitation  to  simple  por- 
traits dictated  by  the  use  of  the  selenium  instru- 
ments was  felt,  and  with  the  introduction  of  the 
telautograph  a  new  and  commercial  field  of  work 
was  opened  up.  There  are  doubtless  a  great 
number  of  important  or  interesting  men  and 
women  in  the  world,  but  there  are  every  day 
hundreds  of  interesting  "  news  snapshots/'  and 
while  portraits  of  the  former  become  more  or  less 
exhausted  at  times,  the  "  photo  dj actualite  "  is 
always  obtainable  and  commands  interest. 

The  first  function  of  the  telautograph  was  to 
telegraph  sketches  or  drawings  in  line,  the  sketches 


62 


PHOTO-TELEGRAPHY 


being  drawn  with  a  pen  and  some  ink  that  was 
essentially  an  electric  insulator  upon  a  metal  base. 
Thus  the  first  materials  sent  to  me  by  Professor 
Korn  were  some  sheets  of  copper  foil,  a  quill  pen 
and  some  ink  composed  of  an  alcoholic  solution  of 
shellac  strongly  tinted  with  a  violet  aniline  dye. 
Now,  if  we  draw  a  sketch  on  copper  with  this  ink, 
and  connect  the  under  side  of  it,  i.e.,  the  plain 


FIG.  28. 

copper  side,  with  one  pole  of  an  electric  battery  B 
(see  Fig.  28),  the  other  pole  of  which  is  connected 
to  one  terminal  of  a  galvanometer  G,  and  we 
connect  the  other  galvanometer  terminal  with  a 
pen  P,  this  consisting  of,  say,  a  darning  needle, 
and  we  now  draw  the  "  pen  "  slowly  over  the  surface 
of  the  sketch,  we  shall  see  that  whenever  the  pen 
crosses  a  line  of  the  drawing,  i.e.,  a  shellac  line, 
the  galvanometer  needle  is  at  zero,  while  when  the 
pen  is  in  contact  with  the  bare  metal — correspond- 
ing to  the  paper  of  an  ordinary  sketch — the  galva- 
nometer needle  is  deflected. 


THE   TELAUTOGRAPH 


In  this  simple  experiment  you  see  the  whole  prin- 
ciple of  the  telautograph,  essentially  different  from 
the  system  described  in  Chapter  II.  ;  the  galvano- 
meter G  represents  the  receiving  apparatus,  the 
sketch  on  copper  and  the  needle  tracing  over  it 
represent  the  transmitter.  We  shall  now  see  how 
this  system  works  out  in  practice.  A  diagram- 


BE 


i— 


(NJIIIW.  :  £1 


\w 


FIG.  29. 

matic  representation  of  the  transmitter  is  shown  in 
Fig.  29. 

On  a  substantial  iron  base  two  uprights  are 
fixed,  and  the  metal  drum  D  fits  on  flanges  on 
a  steel  shaft  which  turns  between  centres  ;  this 
cylinder  is  turned  true  in  the  lathe.  Along  the 
top  is  a  cylindrical  steel  bar  FG,  and  over  this 
slides  a  substantial  tube  PQ  to  which  is  fitted 
the  carrier  of  the  steel  "pen"  or  stylus.  An 
arm  fitted  with  a  half -nut  N  projects  from  one  end 
of  the  tube,  and  the  right-hand  part  of  the  steel 


64  PHOTO-TELEGRAPHY 

shaft  is  cut  with  a  thread,  about  20  threads  per 
centimetre  ;  W  represents  the  cog  wheel  of  the 
motive  arrangement,  so  that  as  the  shaft  turns  the 
nut  N  slides  along  and  so  imparts  to  the  stylus  S  a 
lateral  motion,  hence  the  stylus  traces  a  spiral  path 
over  the  surface  of  the  picture,  which  is  fixed  round 
the  revolving  drum  D. 

The  motive  power  is  again  a  motor  with  two 
slip  rings  fitted  to  the  armature,  so  that  alternating 
current  is  generated  for  the  actuation  of  a  frequency 
meter.  The  motor  turns  at  3,000  revolutions  per 
minute,  and  the  speed  is  geared  down  so  that  the 
cylinder  revolves  once  in  two  seconds.  As  the 
receiving  apparatus  is  placed  on  the  same  table  as 
the  transmitter,  and  contains  as  its  essential  part 
the  string  or  Einthoven  galvanometer,  it  was  found 
necessary  to  mount  the  motor  on  a  separate  stand 
and  to  connect  it  with  flexible  shafting.  In  the 
most  recent  apparatus  the  motor  and  gear  box  are 
mounted  together  on  a  stand  fixed  rigidly  to  the 
wall,  and  flexible  shafting  connects  the  gear  box 
with  the  cog  wheel  that  engages  with  the  wheel  W 
shown  in  the  diagram. 

The  dimensions  of  the  cylinders  used  at  London 
and  Manchester  are  63*5  mm.  diameter  and 
130  mm.  length.  In  the  apparatus  first  installed 
by  Professor  Korn  at  Berlin  and  Paris  he  employed 
a  small  cylinder  the  same  size  as  the  receiving 
drum,  but  it  is  a  considerable  advantage  to  have 


THE   STYLUS  65 

the  transmitting  cylinder  double  the  size  of  that 
used  in  the  reception. 

The  stylus  consists  essentially  of  a  finely -pointed 
needle,  and  ordinary  gramophone  needles  set  in 
a  suitable  holder  have  been  used  with  success  ;  the 
best  form  of  stylus  is  one  originally  designed  by 
Mr.  Sanger  Shepherd,  and  its  form  is  indicated  in 
the  diagram.  The  stylus,  made  of  steel  or  other 
suitable  material,  is  of  the  shape  shown,  and  has  a 
small  tube  put  through  it  about  the  middle,  which 
acts  as  an  axis.  Two  needle-point 
bearings  fit  into  this  finely-drilled 
tube,  so  that  it  is  free  to  turn  with 
minimum  friction  ;  one  end  of  the 
stylus  is  bent  downwards  and  is 
pointed  sharply,  the  other  has  a  hole  through  it  to 
which  is  attached  a  tension  spring,  so  that  the 
pressure  of  the  style  on  the  cylinder  can  be  regulated. 
The  sparking  at  the  point  of  contact  is  apt,  if  not 
sufficiently  well  overcome,  to  quickly  blunt  the  stylus, 
and  Mr.  Shepherd  prepared  several  with  iridium 
points  let  into  the  steel  "  head  "  ;  these  proved  very 
satisfactory,  but  were  eventually  replaced  by  a 
modification  which  was  designed  to  facilitate  the  trial 
of  needles  of  various  materials,  working  at  different 
angles  to  the  surface  of  the  drum.  This  design  is 
shown  in  Fig.  30. 

Here  H  is  the  head  of  the  stylus,  drilled  so  that  a 
needle  AB  can  be  fitted  into  it  and  clamped  by  the 

P.T.  F 


66  PHOTO-TELEGRAPHY 

screw  S ;  TT  is  the  finely-drilled  tube  into  the  ends 
of  which  the  needle  points  fit.  Steel  needles,  sharply 
pointed,  are  at  present  in  use  in  these  holders,  and 
the  tension  is  set  such  that  the  point  does  not  scratch 
soft  lead  foil  when  attached  to  the  drum. 

These  remarks  regarding  the  stylus  apply  to  the 
Daily  Mirror  machines,  a  somewhat  different 
arrangement  being  employed  by  Professor  Korn. 
The  mechanism  of  the  stylus  is,  however,  a  matter 
of  the  greatest  importance,  as  is  also  the  shape  of 
its  point  and  the  angle  that  it  makes  with,  the  surface 
of  the  drum. 

The  sparking  at  the  point  of  contact  of  stylus 
with  copper  foil  sketch  may  be  almost  overcome 
by  shunting  across  it  a  condenser  of  about  i  to  1*5 
microfarad  capacity ;  the  extent  of  sparking  is  pro- 
bably dependent  to  some  extent  on  the  self-induc- 
tion of  the  line  and  may  not  therefore  be  always 
equal.  Sodium  sulphate  cells  have  been  used  by 
Korn  with  great  success  also. 

A  battery  of  from  30  to  60  volts  is  usually 
employed  at  the  sending  station,  and  the  amount 
of  current  received  at  London  from  Paris  averages 
between  6  and  1 2  milliamperes  ;  from  Manchester 
between  9  and  18  milliamperes. 

The  function  of  the  transmitter  is  clearly  to  send 
an  electric  current  to  the  receiver,  which  is  broken 
constantly,  the  duration  of  the  brakes  depending  on 
the  width  of  the  shellac  lines  of  which  the  sketch 


THE   TELAUTOGRAPH 


67 


is  constituted.  We  shall  now  see  how  this  inter- 
mittent current  is  utilised  to  form  a  photographic 
image  in  the  receiving  apparatus. 

Fig.  31  gives  a  diagrammatic  representation  of 
the  sending  and  receiving  stations .  At  the  former 
we  have  the  drum  D  and  stylus  S  and  the  battery  B. 
At  the  receiving  station  we  have  a  drum  DI  half  the 
size  of  the  transmitting  drum,  so  that  the  received 


Sending 
Station 


Receiving 
Station 


FIG.  31. 


picture  is  one-quarter  the  size  of  the  sketch  trans- 
mitted. This  drum  revolves  in  a  light-tight  box, 
and  is  fitted  with  a  steel  shaft  cut  with  a  screw 
thread  100  to  the  inch,  or  about  four  to  the 
millimetre.  The  shaft  turns  in  a  fixed  nut,  so  that 
a  lateral  motion  is  given  to  the  revolving  drum, 
its  motion  thus  corresponding  precisely  to,  that  .of 
the  transmitting  cylinder.  A  sliding  lens  is  fitted 
in  the  centre  of  the  front  of  the  "  dark  box,"  and 
in  front  of  it  is  placed  an  ebonite  screen,  with  an 
adjustable  slit  fitted  centrally  and  opposite  the  lens. 
Any  light  passing  through  the  slit  is  focussed  by 
the  lens  as  a  small  spot  of  light  on  DI,  and  if  the  slit 

K  9. 


68  PHOTO-TELEGRAPHY 

were  always  illuminated  by  a  constant  amount  of 
light,  a  sensitive  photographic  film  wrapped  round 
the  drum  DI  would  receive  a  long,  thin,  spiral  line  of 
exposure . 

Now,  however,  imagine  a  line  drawn  from  the 
centre  of  the  filament  of  the  Nernst  lamp  N  to  the 
slit,  this  line  produced  coinciding  with  the  optic 
axis  of  the  small  sliding  lens  in  the  dark  box.  A 
condensing  lens  C  projects  the  light  from  N  upon 
the  ebonite  screen  in  which  the  slit  is  fitted. 

The  light  passes  through  holes  bored  in  the  pole- 
pieces  of  a  powerful  electro -magnet  M,  across  the 
field  of  which  is  stretched  a  single  flat  silver  wire 
WW,  and  the  shadow  of  this  wire  is  thrown  sharply 
over  the  slit,  the  adjustment  being  carried  out  by 
means  of  the  sliding  lens  L.  The  magnet  is  excited 
by  1 1  o  volts  i  ampere  from  a  battery  of  secondary 
cells,  and  the  current  from  the  connecting  telephone 
line  is  passed  through  WW. 

When  current  flows,  this  wire  is  laterally  dis- 
placed, and  consequently  its  shadow  rises  above  the 
slit  and  allows  the  light  from  N  to  reach  the 
sensitive  film  on  DI.  Should  the  current  received 
be  more  than  is  required  just  to  uncover  the  slit, 
the  necessary  amount  of  extra  resistance  may  be 
inserted  in  series  with  the  line. 

A  small  battery  opposing  the  line  current  may  be 
inserted  at  E  as  shown,  and  a  regulating  resistance 
R  shunted  across  the  galvanometer.  By  means  of 


THE    BACK    CURRENT  69 

the  latter  the  movement  of  the  wire  WW  can  be 
readily  controlled,  for  if  the  line  resistance  be  w\ 
and  the  resistance  at  R  be  w2,  then  the  ratio  of  the 
current  entering  the  "  string  "  WW  to  that 

absorbed  by  the  shunted  resistance  will  be  — .     In 

w\ 

considering  displacements  of  the  string  which  are 
very  small  compared  with  its  length,  we  may  regard 
the  displacement  as  proportional  to  the  current. 
Hence,  by  varying  w%,  w\  remaining  constant,  the 
displacement  can  either  be  regulated  to  work  with 
a  slit  of  any  desired  width  or  to  accommodate  a 
current  received  of  any  strength,  the  width  of  slit 
remaining  constant. 

In  much  of  the  work  the  battery  E  was  put  in 
series  with  the  resistance  R,  so  that  current  flowed 
continuously  through  the  string  and  gave  it  a  dis- 
placement opposite  in  direction  to  that  caused  by 
the  line  current.  This  procedure  conduces  to 
"  dead-beatness,"  and  it  brings  the  string  back  to 
the  zero  position  very  rapidly  the  moment  the  line 
current  is  interrupted.  The  ratio  of  the  "  reverse  " 
current  to  the  "  line  "  current  is  best  varied  to  suit 
the  circumstances,  but  if  the  latter  be  fairly  uniform, 
the  most  desirable  plan  from  the  operator's  point 
of  view  is  to  keep  E  and  R  constant,  and  to  adjust 
the  movement  in  the  string  caused  by  the  line 
current  by  means  of  a  regulating  resistance  in  series 
with  the  line. 


70  PHOTO-TELEGRAPHY 

The  currents  transmitted  by  this  system  being 
considerably  greater  than  those  practicable  with  the 
selenium  apparatus  a  somewhat  different  system  of 
synchronising  the  two  instruments  is  required. 
It  becomes  necessary,  in  fact,  to  reverse  the  direc- 
tion of  the  current  at  the  moment  of  synchronising. 
The  drum  of  the  receiving  apparatus  is  revolved 
about  i  per  cent,  faster  than  the  transmitting  drum, 
and  finishes  its  revolution  rather  before  the  trans  - 


N 


mitter,  as  in  the  case  of  the  selenium  machines. 
When  the  turn  is  completed  the  drum  is  checked  by 
a  metal  stop,  and  the  galvanometer  circuit  auto- 
matically thrown  out,  a  relay  circuit  being  switched 
in  in  its  place.  The  transmitting  drum  on  com- 
pleting its  turn  causes  a  fleeting  contact  to  be  made 
in  the  reverse  direction  to  that  of  the  line  current, 
and  this  actuates  the  relay,  which,  being  polarised, 
is  only  sensitive  to  current  in  the  one  direction. 
The  relay  closes  the  local  circuit  which  removes 
the  check  by  means  of  an  electro -magnet,  and  both 


CURRENT   REVERSERS  71 

drums  therefore  start  off  on  a  fresh  revolution  in 
unison. 

The  reverser  is  of  various  forms,  and  is,  of 
course,  used  in  most  electrical  instruments  which 
require  similar  synchronisation.  One  pattern  of  it 
is  seen  in  Fig.  32.  Here,  M,  N  are  two  steel 
tongues  with  platinum  contacts  attached  to  a  bar 
which  can  rotate  about  a  fulcrum1  F  ;  it  is  held  in 
position  by  a  spring  S,  the  end  of  which  is  attached 


, 

>           1 

j,  -i 

f       \  \ 

FIG.  33. 

to  a  point  T,  in  this  case  in  the  bed -plate. 
A  represents  a  projecting  pin  on  the  cylinder  or 
drum,  which,  in  the  position  shown,  depresses  the 
end  of  the  bar  and  consequently  causes  the  tongues 
M,  N  to  rise.  As  soon  as  the  drum  has  travelled  a 
little  further  round,  the  pin  A  is  out  of  the  way, 
hence  the  spring  S  pulls  the  tongues  M,  N  down 
again  into  their  normal  position. 

The  next  diagram  (Fig.  33)  represents  the  revers- 
ing arrangement.  M,  N  are  again  the  tongues, 
while  P,  Q  and  R,  S  are  four  platinum  contact  pins. 


72  PHOTO-TELEGRAPHY 

In  the  normal  position  of  the  springs  they  press 
against  the  pins  R,  S,  which  are  connected  in  the 
manner  shown  to  the  terminals  of  the  "  line." 
When  the  synchronising  pin  comes  into  contact 
with  the  bar  the  tongues  are  raised  into  close 
contact  with  the  pins  P,  Q,  so  that  clearly  the 
polarity  at  the  line  terminals  is  reversed.  P,  Q  are 
the  receiving  circuit  relay  pins  of  the  transmitter, 
while  R,  S  are  for  the  galvanometer  circuit. 

Towards  the  end  of  the  year  1908  Professor  Korn 
installed  one  of  his  telautographs  at  the  offices  of 
L' Illustration  in  Paris,  another  being  at  the  Lokal 
Anzeiger  offices  in  Berlin,  under  the  supervision  of 
his  colleague,  Dr.  Glatzel,  and  a  sketch  was  trans- 
mitted with  considerable  success,  the  subject  being 
that  of  an  aeroplane  flight.  The  subject  was 
topical,  and  the  picture  was  published  the  following 
morning  in  Le  Matin,  with  an  article,  descriptive 
of  the  event,  entitled  "  Prodigious."  And  considering 
the  fact  that  a  complicated  news  picture  had  been 
wired  some  800  miles  in  ten  minutes,  that  would 
have  taken  several  hours  to  come  by  train,  for 
the  first  time  in  history,  the  enthusiasm  of  the 
Matin  was  certainly  justified.  I  arrived  in  Paris 
the.  following  morning  and  saw  large  crowds 
of  people  looking  at  the  photographic  print, 
which  was  displayed  in  the  way  customary  with 
the  Matin  in  their  windows  facing  the  Boule- 
varde.  A  few  days  later  a  telautograph  was  being 


TELAUTOGRAPH  EXPERIMENTS       73 

constructed  by  Mr.  Sanger  Shepherd  for  the  Daily 
Mirror,  and  every  effort  was  made  to  finish  it  in 
time  for  the  King's  visit  in  January,  1 909,  to  Berlin. 
Pictures  were  wired  from  Berlin  to  Paris  of  His 
Majesty  driving  through  the  streets  of  Berlin,  and 
from  those  further  pictures  were  prepared  by  M. 
Chatenet,  which  he  attempted  to  re -transmit  from 
Paris  to  London.  But  the  London  telautograph 
had  only  been  tested  a  day  or  two  previously,  and 
was  not  in  anything  approaching  good  adjustment, 
and  the  results  were  not  good  enough  for  publica- 
tion. This  was  after  attempting  the  transmissions 
from  about  i  A.M.  to  3  A.M.  Results  soon  began 
to  come  through  with  regularity,  however,  and  the 
telautograph  became  a  useful  means  of  obtaining 
news  pictures  from  the  Continent. 

An  interesting  break  in  the  telautograph  trans- 
missions was  caused  by  the  great  Postal  strike  in 
France,  which  was  at  its  worst  during  the  summer 
of  1909.  The  pressure  on  the  telephone  lines  was 
very  great  at  this  time,  as  so  much  correspondence 
was  carried  on  by  means  of  the  telephone,  and  it  was 
only  occasionally  that  the  Post  Office  was  able  to 
spare  a  line  for  the  photo -telegraphic  work.  On 
one  occasion  a  picture  was  being  transmitted,  and 
the  adjustments  had  taken  a  minute  or  two  longer 
than  usual  ;  the  line  could  only  be  spared  for  about 
fifteen  minutes,  and  when  this  time  had  elapsed  the 
officials  were  obliged  to  cut  our  line.  The  picture 


74  PHOTO-TELEGRAPHY 

was  only  about  two -thirds  transmitted,  and  the 
result  was  that  the  photograph  was  only  received  in 
part  ;  needless  to  say,  the  more  important  part  of 
the  subject  was  missing,  and  the  result  was  quite 
useless  for  publication. 

Experiments  were  carried  out  between  Berlin  and 
Paris,  using  one  line  only  and  an  earth  "  return  "  ; 
the  current  received  in  this  way  was  about  5  milli- 
amperes,  and  sufficient  to  work  the  apparatus  satis- 
factorily. 

A  second  English  telautograph  was  begun  in 
February,  and  an  effort  was  made  to  have  it  ready 
and  installed  at  Manchester  in  time  to  telegraph 
down  to  London  the  finish  of  the  Grand  National 
race  at  Aintree  in  March.  A  change  was  made  at 
the  same  time  in  Manchester,  the  photo -telegraphic 
installation  being  removed  from  the  office  of  the 
Manchester  Courier  to  a  new  office  specially 
equipped  for  the  work.  A  few  days  before  the  race 
took  place  the  new  telautograph  was  taken  to  Man- 
chester, and  through  the  courtesy  of  the  Post  Office 
officials  there  a  trunk  line  was  put  in  and  tested  just 
in  time  to  enable  one  experimental  picture  to  be 
wired  through.  The  finish  of  the  race  was  taken 
by  a  press  photographer,  and  the  plate  taken  by  a 
Daily  Mirror  motor  car  to  the  station  at  Aintree, 
and  brought  thence  by  train  to  Manchester.  It 
was  then  developed  and  a  fish-glue  print  of  the 
picture  was  prepared  and  at  once  wired  to  London. 


ADVANTAGES  OF  TELAUTOGRAPH  75 

Such  instances  as  this  show  how  by  means  of 
photo -telegraphy  a  newspaper  can  publish  a  picture 
of  some  event  a  clear  day  before  another  paper.  A 
few  critics  are  still  sceptical,  and  say  :  "  Would 
not  the  public  prefer  to  wait  the  extra  day  and  have 


FIG.  34. — Reception  to  Sven  Hedin,  wired  from  Paris 
to  London  by  Telautograph. 

a  better  picture — the  original?  '  The  answer  is  : 
"  No."  Just  as  the  public  prefer  to  have  a  brief 
telegram  about  an  important  event  rather  than  wait 
another  day  for  the  full  report,  so  they  prefer 
to  have  a  graphic  representation,  i.e.,  a  photo- 
graph, immediately.  The  advantage  to  the  Daily 
Mirror  of  having  interesting  pictures  by  wire  before 


76  PHOTO-TELEGRAPHY 

any  other  paper  is,  in  fact,  obvious.  During  the 
great  trial  of  Madame  Steinheil  photographs  that 
had  been  taken  in  court  late  in  the  afternoon  were 
telegraphed  to  London  soon  after  7  o'clock.  The 
time  of  preparation  of  the  photographs  is,  of  course, 
a  factor  of  importance  ;  in  the  earlier  days  it  was 
customary  for  an  artist  to  draw  a  line  sketch  of  the 
photograph  to  be  telegraphed,  and  this  sketch  was 
then  copied  in  the  camera,  and  a  fish-glue  print 
made  from  the  negative  on  copper  foil.  But 
various  improvements  in  the  apparatus  have  gradu- 
ally rendered  possible  the  transmission  of  half-tone 
photographs,  and  thus  the  work  of  the  artist  is 
done  away  with,  together  with  his  time. 

The  preparation  of  these  half-tone  photographs 
will  be  more  fully  considered  in  the  chapter  dealing 
with  the  telectrograph,  but  mention  may  here  be 
made  of  the  work  done  by  M.  Chatenet,  which  has 
helped  considerably  in  determining  the  best  means 
of  producing  them. 

The  progress  in  transmission  has  been  due,  as 
stated  above,  to  continual  small  improvements  in 
the  apparatus.  The  galvanometer  is  the  most 
delicate,  as  well  as  the  most  vital,  part  of  the  instru- 
ment, and  it  is  the  greater  perfection  of  the  moving 
part  of  the  galvanometer  that  has  contributed  to 
the  improved  nature  of  the  results. 

A  very  small  period  is  necessary  in  the  "  string/' 
and  its  weight  must  be  very  small  and  its  strength 


THE    GALVANOMETER 


77 


comparatively  great.      A  flat  silver  string  appears 
to    be   more   rapid   than   any   form   of   phosphor- 


FIG.  35.— Example  ot  Fashion  Plate  wired  by  the 
Korn  Telautograph. 

bronze,  and  the  length  of  it  free  to  swing  is  usually 
about  5  cm.     An  improvement  introduced  recently 


78  PHOTO-TELEGRAPHY 

by  Professor  Korn  is  to  have  a  flat  string  slightly 
twisted,  and  the  most  recent  galvanometers  have 
been  provided  with  a  collar,  which  can  be  turned 
through  a  small  angle,  and  this  has  a  micrometer 
scale  to  it,  so  that  the  angle  through  which  the 
ribbon  is  twisted  can  be  accurately  determined. 

By  using  a  wide  slit  in  front  of  the  receiving 
box  so  that  more  light  is  admitted  to  the  receiving 
drum,  with  a  consequent  larger  movement  of  the 
shadow  of  the  ribbon  or  string,  it  is  possible  to 
receive  the  picture  direct  on  photographic  paper. 
This  is  important,  as  it  saves  one  operation  in  the 
photographic  work,  and  a  minute  or  two  fre- 
quently decides  whether  a  picture  can  be  "  got 
in  "  an  early  edition  of  the  paper  or  not. 

The  inertia  of  the  photographic  sensitive  film 
plays  an  interesting  part  in  the  more  brilliant 
results  obtained  direct  on  sensitive  paper.  When 
the  wider  slit  is  used  the  tension  of  the  galvano- 
meter string  is  made  less  so  that  the  shadow 
will  rise  to  the  necessary  extent  to  quite  open 
the  slit.  As  it  rises  and  falls  each  time  there 
is  a  current  sent  through  the  string,  the  light 
is  obviously  greatest  at  the  moment  when  the 
slit  is  totally  uncovered  and  is  least  at  the  two 
instants  when  the  slit  is  just  a  little  opened  and 
nearly  closed.  Now  before  light  can  produce  a 
developable  effect  in  a  photographic  film  it  has  to 
overcome  the  chemical  inertia  of  the  film,  and  unless 


DUPLEX   TRANSMISSIONS 


79 


it  be  of  sufficient  intensity  to  do  this,  nothing  is 
obtained  on  development.  The  result  is  that  if  the 
complete  upward  and  backward  displacement  of 
the  string  takes  a  time  T,  and  during  that  time 
the  sensitive  film  on  the  revolving  drum  is  travel- 
ling with  a  velocity  v,  the  length  of  the  mark 
produced  on  development  will  not  be  rT,  but 
will  be  vt,  where  t  <;  T  and  the  distance  v  (T—t) 


To  Earth 


To  Earth 


To  Earth 


To  Earth 


FIG.  36. 


corresponds  to  the  inertia  of  the  film.  Con- 
sequently the  darkest  parts  only  of  the  component 
dots  of  the  picture  are  given  in  the  developed  print, 
and  there  is  more  contrast  in  the  picture. 

Simultaneous  transmissions  in  two  directions 
have  been  recently  suggested  by  Professor  Korn, 
which  would  reduce  the  cost  of  photo -telegraphy, 
and  save  operators'  time  as  well.  The  scheme  is 
seen  at  a  glance  in  Fig.  36.  The  parallel  lines 
represent  the  telephone  lines  between  the  two 
stations.  AI  is  the  transmitting  flrum  of  one 
machine,  GI  the  string  galvanometer;  A2  and  G2 


8o  PHOTO-TELEGRAPHY 

are  the  similar  parts  of  the  other  instrument.  One 
wire  of  the  telephone  line  is  used  in  each  case  for 
the  return,  the  current  flowing  through  the  earth. 
This  method  has  not  so  far  been  practically  tested, 
but  will  doubtless  be  useful  when  a  greater  number 
of  photographs  are  transmitted. 

The  question  of  the  greatest  possible  length  of 
transmission  by  the  telautograph  is  daily  becoming 
more  important.  In  1 908  an  experiment  was  made 
with  Korn's  selenium  machines  between  Berlin  and 
London,  the  two  lines  Berlin -Paris  and  Paris  - 
London  being  joined  at  Paris  by  M.  Chatenet,  who 
acted  as  "  intermediary."  This  was  necessary 
owing  to  the  impossibility  of  speaking  clearly  from 
Berlin  to  London  ;  anything  spoken  had  therefore 
to  be  said  to  the  Paris  operator,  who  "  passed  it  on  " 
to  the  Berlin  operator,  and  vice  versa.  Then, 
when  the  adjustments  were  made,  the  Paris 
operator  simply  connected  up  the  Berlin -Paris  and 
Paris -London  lines  on  his  switchboard. 

These  experiments  were,  as  already  stated, 
carried  out  with  the  selenium  apparatus,  and  the 
current  received  at  London,  about  0*25  milliampere, 
was  insufficient  to  work  with.  The  stronger  cur- 
rent for  the  synchronising  was  sufficient  to  work 
the  relay,  however,  and  as  it  is  of  the  same  mag- 
nitude as  the  galvanometer  current  used  in  the 
telautograph  there  is  little  doubt  but  that  the  latter 
instrument  could  be  worked  effectually  between 


LENGTH   OF  TRANSMISSION 


81 


Berlin  and  London,  and  probably  over  distances 
up  to  1,500  miles. 


O. 


<D 

d 


Beyond  this  stage  it  would  be  necessary  to  have  a 
more  sensitive  relay  for  the  synchronising,  and  a 
more  sensitive  galvanometer.  The  latter  is  as  easy 

P.T.  G 


82  PHOTO-TELEGRAPHY 

of  accomplishment  as  the  former.  The  silver  string 
in  the  galvanometer  can  be  made  finer  ;  I  have 
obtained  them  in  this  country  less  than  2^00^  incri  in 
diameter.,  while  by  using  the  silvered  quartz  threads 
suggested  by  Duddell  for  the  Einthoven  galvano- 
meter a  thread  j^Joo^h  incn  diameter  can  be 
employed.  The  magnetic  field  can  also  be  greatly 
increased  by  building  the  magnets  considerably 
larger  and  making  the  windings  take  enough 
current  for  complete  saturation  of  the  iron.  The 
instrument  then  becomes  exceedingly  sensitive, 
and  it  merely  remains  for  the  optical  parts  to  be 
suitably  constructed. 

As  explained  elsewhere,  the  string  of  the  galva- 
nometer should  have  a  period  which  is  neither  equal 
to  nor  a  multiple  nor  sub -multiple  of  the  period  of 
the  interruptions  due  to  the  transmitting  apparatus  ; 
this  applies  only  to  the  transmission  of  half- 
tone line  photographs,  which  consist  of  a  definite 
number  of  lines  per  unit  of  length.  The  natural 
period  of  the  string  can  be  varied  in  several  ways. 
It  can  most  readily  be  measured  by  means  of  the 
recording  apparatus  described  in  Chapter  V.  If 
a  short  current  be  sent  through  the  string  by  means 
of  suddenly  tapping  a  Morse  key,  a  jerk  is  given  to 
it  and  it  is  displaced  through  a  distance  d  (at  the 
centre).  It  then  swings  back  to  zero  and  then  past 
the  zero  point,  to  a  point  distant  d  —  x  from  it 
where  d  —  x  is  less  than  d.  One  has,  in  fact,  a 


PERIOD    OF   STRING  83 

damped  oscillation,  and  the  string  does  not  actually 
come  to  rest  for  a  definite  time.     During  this  time  t 


m 


FIG.  38. — Example  of  line  sketch  from  photograph,  wired 
by  the  Korn  Telautograph  from  Paris  to  London. 

there  may  be  n  complete  vibrations,  from  which  the 
natural  period  tjn  can  be  ascertained.  If  the  string 
be  made  to  cast  a  shadow  over  an  illuminated 
slit  through  which  the  light  passes  when  it  is 

G  2 


84  PHOTO-TELEGRAPHY 

displaced,  and  this  light  fall  on  a  rapidly  travelling 
band  of  photographic  film,  and  a  tap  be  then  given 
with  the  Morse  key  as  above  described,  a  record  of 
the' movements  of  the  string  is  obtained.  If  the 
rate  at  which  the  film  travels  be  known,  it  is  easy  to 
calculate  the  period  of  the  galvanometer. 

The  string  has  a  shorter  period  if  its  length  be 
shortened  or  its  tension  increased,  and  the  damping 
of  its  oscillations  can  be  effectually  increased  if  a 
twist  be  given  to  one  end  of  it  in  the  manner 
already  indicated.  The  effect  of  damping  can  be 
seen  if  we  consider  the  equation  of  the  move- 
ment of  the  string,  which  is  of  the  form 

d  =  ae~kt  cos  (nt  -f-  a)> 

where  d  is  the  displacement ;  ae  ~kt  decreases  as 
t  increases ;  k  is  the  damping  constant,  and  e~kt  the 
damping  factor.  K  has  got  to  be  as  large  as  pos- 
sible, and  can  be  made  large  if  we  increase  the 
friction  at  the  ends  of  the  string.  Suppose  the 
string  to  be  displaced  still  through  the  distance  d, 
where  /  is  the  elastic  force,  the  work  done  is  df  ; 
this  is  the  measure  of  the  potential  energy  of  the 
centre  of  the  string,  provided  we  subtract  /,  the 
loss  of  energy  through  heating  owing  to  the 
friction  ;  I  increases  as  /  is  increased,  while  d 
is  diminished  for  the  same  amount  of  current  sent 
through  the  string. 

The  rapiditv  of  damping  is  readily  seen  from  the 
diagram  shown  in  Fig.  39,  which  is  drawn  to  scale 


PERIOD    OF    STRING  85 

from   an   actual   photographic   record   of   a   short 
current  sent  through  the  galvanometer. 

Returning  now  to  the  question  of  possible  dis- 
tance of  transmission,  it  is  clear  that  for  a  very 
sensitive  galvanometer  the  displacement  for  the 
same  current  would  require  to  be  much  greater  ; 
the  period  would  be  lengthened,  /  and  /  dimin- 
ished, and  the  rate  of  working  diminished  also  ; 
with  a  silvered  quartz  fibre,  the  period  would  be 
much  longer  than  that  of  the  flat  silver  ribbon  now 


FIG.  39. — Damping  of  oscillograph  string.     The  ordinates 
represent  the  displacement,  d. 

in  use,  and  the  transmission  would  therefore  be  of 
an  altogether  slower  nature.  The  capacity  of  a 
long  line  would  be  correspondingly  higher,  and 
this  would  again  necessitate  slowness  in  the  trans- 
mission. 

The  theoretical  limits  of  distance  of  transmission 
are  fairly  wide,  but  the  practical  limits  are  unfortu- 
nately very  different.  Yet  such  distances  as  those 
between  London  and  Rome,  London  and  Marseilles, 
etc.,  should  be  by  no  means  insuperable. 

That  the  telautograph  could  be  put  to  other  uses 
than  that  of  transmitting  photographs  is  seen 
from  its  ability  to  transmit  writing.  Written 


86  PHOTO-TELEGRAPHY 

matter  comes  out  very  clearly  in  the  received  pic- 


FIG.  40. — Example  of  half-tone  photograph  transmitted 
from  Berlin  to  Paris  by  Telautograph. 

tures,  as  do  maps  and  diagrams  of  all  kinds.      In 
the  case  of  typewritten  matter,  for  which  a  blue 


TELEGRAPHING    WRITING  87 

or  violet  ink  is  usually  employed,  it  is  necessary  to 
make  a  photographic  negative,  using  an  ortho- 
chromatic  plate  and  a  yellow  contrast  filter  in 
front  of  the  camera  lens.  The  writing  then 
appears  colourless  in  the  negative,  and  hence  dense 
"  black  "  in  the  fish-glue  print  made  from  it.  Type- 
written matter  has  been  telegraphed  successfully 
from  Paris  to  London. 

It  will  thus  be  seen  that  a  signature  for  banking 
purposes  could  be  sent  by  wire,  the  signature  being 
written  direct  in  the  shellac  ink  upon  a  clean  sheet 
of  copper  or  lead  foil.  This,  by  the  way,  must  be 
scrupulously  clean,  and  for  the  copper  a  weak  solu- 
tion of  potassium  cyanide  may  be  used  with  advan- 
tage. Another  method  is  to  rub  the  metal  with  a 
cloth  and  some  finely -powdered  pumice-stone.  The 
telegraphy  of  signatures  for  identification  purposes 
may  be  an  important  feature  of  later  work. 

The  telautograph  may  be  said  to  have  solved  the 
problem  of  commercial  photo -telegraphy,  and  to 
have  directly  stimulated  the  efforts  of  others  who 
may  have  contributed  to  the  development  of  the 
work,  or  who  may  be  now  endeavouring  to  con- 
tribute to  it  in  the  future. 


CHAPTER    IV. 

THE  THORNE  -  BAKER  SYSTEM  —  DIFFERENCES 
BETWEEN  THE  TELECTROGRAPH  AND  EAR- 
LIER CHEMICAL  SYSTEMS— ^ELECTROLYTIC 
RECORDS  OF  CURRENTS  TRANSMITTED 
THROUGH  LONG  CABLES  —  THE  THORNE- 
BAKER  LINE-BALANCE—WORK  WITH  THE 
ELECTROLYTIC  TELECTROGRAPH. 

THE  simplest  and  most  practical  apparatus  for 
photo -telegraphy  at  the  present  time  is  fairly 
admitted  to  be  the  telectrograph,  which  came 
into  use  by  the  Daily  Mirror  in  July,  1909. 
It  was  seen  in  the  first  chapter  that  Bakewell 
had  obtained  some  promising  results  with  his 
chemical  telautograph,  in  which  he  used  a  picture 
produced  in  lines  on  a  metal  foil,  the  lines  being 
of  an  insulating  character  such  as  offered  by  shellac, 
gum,  or  glue,  etc. 

One  of  his  chief  difficulties  was  found  in  the 
synchronism,  yet  results  were  obtained,  and  some 
of  the  most  interesting  of  these  were  telegraphed 
written  matter.  The  telectrograph,  by  which 


THE   TELECTROGRAPH  89 

name  I  have  designated  my  own  modification 
of  Bakewell's  apparatus,  has  proved  successful, 
because  (i.)  all  the  mechanical  parts  have  been 
most  carefully  modelled  on  lines  dictated  by 
innumerable  failures  and  experiments,  and  (ii.)  by 
means  of  the  line -balancer  I  have  made  the 
receiving  instrument  of  such  a  character  that  the 
distortion,  lag  and  line -surges  met  with  when 
working  with  long-distance  cables  can  be  instantly 
overcome  by  simple  regulation. 

Mr.  Sanger  Shepherd,  whose  workmanship  is 
perhaps  the  most  accurate  and  effectual  of  any 
instrument  maker  in  the  world,  undertook  from 
the  start  the  constructional  work,  and  to  him 
largely  belongs  the  credit  of  the  success  of  the 
Daily  Mirror's  photo -telegraphic  work.  In  trans- 
mitting a  photograph  seven  inches  by  five,  made 
up  of  fifty  lines  to  the  inch,  the  Caselli 
stylus  has  to  traverse  7  X  50  or  350  lines  per 
revolution.  With  one  revolution  of  the  transmit- 
ting drum  in  two  seconds  we  have  175  dots 
per  second  recorded  on  the  receiving  paper.  If 
one  dot  were  j^th  of  a  second  later  than  it  should 
be  it  would  fall  into  line  with  the  dot  of  the  next 
line  in  the  line  photograph.  The  figure  of  merit 
in  synchronisation  requires  to  be  within  an  error 
of  at  least  i  in  500  to  obtain  intelligible  results. 
Thus  the  synchronising  mechanism  lias  to  be  very 
fairly  "  perfect,"  and  it  has  been  necessary  to 


go  PHOTO-TELEGRAPHY 

make  the  balancing  of  the  stylus  and  various  other 
mechanical  details  equally  precise. 

If  we  refer  to  Fig.  I  (Chapter  I.)  we  see  that 
at  the  sending  station  we  have  a  revolving  metal 
drum  A,  to  which  the  lead  foil  half-tone  photo- 
graph is  attached.  This  revolves  while  .  a  stylus 
traces  a  spiral  path  over  the  picture  in  virtue  of 
its  being  given  a  lateral  motion.  The  style  is 
fixed  to  an  arm  (Fig.  28,  Chapter  III.),  which 
has  screwed  to  it  a  half-nut,  threaded  so  as  to 
fit  on  the  shaft  F,  which  is  also  threaded.  Hence 
as  the  shaft  turns,  between  steel  centres,  the 
half-nut  travels  along  it,  and  so  draws  the  stylus 
along  too.  In  the  telectrograph  there  are  75 
threads  to  the  inch,  so  that  the  style  moves  later- 
ally with  a  velocity  of  j^oth  inch  per  second. 

The  style  is  of  special  design,  as  shown  diagram - 
matically  in  Fig.  41,  turning  about  pivots  P  and 
being  provided  with  a  tension  screw  T.  The  point 
of  contact  is  a  V-shaped  iridium  tracer  I,  which 
withstands  the  constant  sparking  caused  by  the 
makes  and  breaks  of  the  current.  The  actual 
point  must  be  very  fine,  yet  not  fine  enough  to 
scratch  the  lead ;  the  tension  is  regulated  by  the 
screw  T. 

The  battery,  usually  100  volts,  consists  of 
secondary  cells,  and  hence  a  series  of  currents 
are  sent  into  the  line  exactly  as  in  the  case  of 
Korn's  telautograph.  At  the  receiving  end  we 


THE   TELECTROGRAPH 


FIG.  41. 


have  a  cylinder  B,  the  same  size  as  A,  and  revolv- 
ing   in    synchronism,    its    movement    being    con- 
trolled   in    the     way     already    described    and    in 
common     use     in     certain 
systems   of    ordinary   tele- 
graphy. 

Round  B  is  wrapped  a 
piece  of  specially  prepared 
paper,  containing  in  its 
composition  certain  chemi- 
cal substances  which  de- 
compose on  the  passage 
through  them  of  an 
electric  current.  The  un- 
decomposed  chemicals  must  be  colourless,  the 
decomposition  products  must  be  coloured.  Hence, 
in  theory,  whenever  a  current  is  sent  from  the  send- 
ing instrument  it  passes  through  the  paper,  via  the 
stylus,  and  a  black  or  coloured  mark  is  made  on 
the  paper,  the  length  of  the  mark,  /,  measured  along 
the  circumference,  being  equal  to  tu,  where  u  = 
the  velocity  of  the  surface  of  the  drum,  and  /  the 
duration  of  the  current.  When,  however,  the  send- 
ing and  receiving  instruments  are  connected  by  a 
long  distance  line,  instead  of  an  ordinary  resistance, 
we  find  that  for  a  current  of  duration  t,  the  length 
of  the  chemical  mark  is  considerably  greater 
than  tu. 

If  we  were  to  send  one  brief  current  from  trans- 


9.2  PHOTO-TELEGRAPHY 

mitting  to  receiving  station,  say  of  ^oo^n  second 
duration,  and  we  were  to  place  a  piece  of  chemically 
sensitive  paper  on  the  receiving  drum,  the  latter 
revolving  in  the  ordinary  way,  we  should  get 
a  mark  of  this  form  ^^,  showing  that  the  line 
takes  an  appeciable  time  tc 
charge  up,  and  when  charged, 
requires  time  again  to  fully 
discharge.  This  can  be  repre- 
sented by  the  curve  shown  in 
Fig.  42.  If  we  were  to  transmit 
several  brief  currents  of  equal 


Tim  e  . 

period,  and  were  then  to  stop 
suddenly,    we     should    get    a 

continuity  of  marking,  not  dying  away  for  an  appre- 
ciable time. 

These  difficulties  can  be  almost  entirely  over- 
come by  the  line  balance  described  by  me  in 
November,  1909,*  in  which  a  current  with  shunt 
capacity  and  an  inductance  to  time  the  phase 
where  necessary  is  sent  into  the  line  to  damp 
down  the  secondary  surges.  The  arrangement 
is  seen  in  Fig.  43.  D  is  the  receiving  drum 
and  S  a  platinum  stylus.  The  shunt  circuit 
consists  of  two  similar  parts,  a  secondary 
cell  being  in  each,  BI  and  B2;  a  variable  induct- 
ance in  each  (not  shown) ;  and  a  variable  resistance 
of  1,000  ohms,  RI  and  R2.  The  ends  of  the  resist- 
*  Journal  of  the  Society  of  Arts,  2975,  30. 


THE    LINE    BALANCER 


93 


ances  are  joined  in  the  manner  shown,  while 
between  the  sliding  contacts  of  the  resistances  is  a 
variable  capacity  K  ;  the  capacity  ranges  from  o 
to  i  microfarad. 

When  a  photograph  is  received  the  waves  sent 
into  the  line  are  distorted  by  their  passage  through 
it,  and  this  distortion  appears  as  an  elongation  of 


Tel  e  ph  on  e 
Lin  e 


FIG.  43. 

the  chemical  dots  or  marks  made  upon  the  paper 
on  the  receiving  drum  as  already  described  ;  the 
greater  the  distortion  the  less  is  the  resistance 
required  in  RI  and  R2 ;  the  greater  the  capacity  of 
the  line  connecting  the  two  machines  tKe  more  the 
capacity  one  must  introduce  by  means  of  K. 

It  can  now  readily  be  seen  how  practical  the 
telectrograph  is  for  commercial  work.  The 
operator  carefully  watches  the  paper  on  the  drum 
during  the  first  two  or  three  revolutions,  and 
according  as  the  marks  are  crisp, or  blurred  he 
varies  the  various  regulating  elements.  Hence 


94  PHOTO-TELEGRAPHY 

before  any  important  portion  of  the  photograph 
has  been  transmitted  he  can  ensure  its  reception 
being  good.  In  any  optical  method  of  reception, 
on  the  other  hand,  should  any  error  have  occurred 
in  the  preliminary  adjustments,  the  operator  cannot 
know  of  his  fault  until  after  both  the  reception  has 


FIG.  44. — i.  Capacity  on  line.  2.  No  capacity.  3.  Capacity 
on  line,  but  balancer  in  shunt. 

Photograph  showing  the  balancing  effect  of  the  Telectrograph 
arrangement.  Currents  were  sent  to  the  receiver  by 
closing  a  circuit  with  a  Morse  key.  The  chemical  marks 
produced  are  elongated  or  "tailed"  when  capacity  is 
shunted  on  the  line  (i).  They  are  short  and  end  abruptly 
with  no  capacity  (2).  The  capacity  effect  is  obviated  by 
the  balancer  (3). 

been  completed  and  the  film  or  sensitive  paper  has 
been  developed.  When  we  remember  that  the  cost 
of  the  telephone  line  between  London  and  Paris  is 
four  shillings  for  three  minutes,  or  over  a  farthing 
a  second,  the  need  for  rapidity  becomes  apparent. 
The  machine  must  be  simple,  rapid,  and,  if  pos- 
sible, certain  ;  the  preliminary  tests  and  adjust- 
ments reduced  to  the  minimum,  and  the  operator 
himself  must  be  quick  and  intelligent,  and  be  able 
to  locate  a  fault  rapidly. 


CAPACITY    EFFECTS  95 

It  is  interesting  to  note  that  the  distortion 
caused  in  transmission  through  a  long  line  or  cable 
is  considerably  lessened  where  there  is  high 
leakance.  Heaviside  has  shown  that  in  telephony 
the  distortion  D  is  given  by  the  equation 

R  S 

=¥T      TK' 

and  the  attenuation  A  by 

R  S 


A- 

- 


where  R  is  resistance,  L  inductance,  K  capacity, 
and  S  leakance.  When  leakance  is  very  small  on 
a  line  of  considerable  weight  we  have  the  dis- 

•p 

tortion  approximately  proportional  to   -^=-. 

2       \-4 

The  capacity  effects  are  thus  less  pronounced 
when  there  is  much  leakance  on  a  line,  if  the  latter 
take  place  at  various  well  distributed  intervals,  as 
its  effect  is  to  obstruct  the  charging  up  of  the  line. 
Capacity  does  not  reduce  the  energy  transmitted 
along  the  line,  but  its  effect,  as  well  known  in  tele- 
phony, is  to  cause  length  of  time  in  discharge  ; 
the  inductance  is  valuable  as  it  counteracts  the 
distortion,  but  it  is  small  in  submarine  and  under- 
ground cables,  because  the  current  flows  through 
the  two  lines,  which-  are  close  together,  in  opposite 
directions,  the  self-i'nduction  of  each  being  thereby 
largely  neutralised  by  the  other. 


96  PHOTO-TELEGRAPHY 

It  is  interesting  to  note  that  often  during  very 
wet  weather  less  "  balancing  "  of  the  line  is  re- 
quired in  working  with  the  telectrograph,  this  bear- 
ing out  the  distortion  expression 

R          S 


2  L      2  K* 

The  capacity  of  a  single  line  of  diameter  d  and 
length  /  at  a  height  H  above  the  ground  is  given 
by  the  following  expression  :— 

r  __  I  X  2*415  X  io6 
~  --       ~~~' 


but  this  becomes  effectively  much  less  where  there 
are  two  lines  close  together.  In  the  case  of  tele- 
phone cables  we  can  divide  the  capacity  of  one  line  by 
two  to  get  the  total  capacity  of  the  closed  line,  since  the 
capacity  of  two  condensers  in  series  is  equal  to  half  that 
of  one  singly.  As  will  be  seen  later,  the  capacity  of 
a  Paris  —  London  single  line  is  10*6  m.f.,  so  that  the 
capacity  of  the  two  lines  forming  a  closed  circuit  is 
5  '3  m.f.  The  submarine  cable  between  Sangatte 
(France)  and  St.  Margaret's  Bay  is  5*52  m.f.  in 
capacity,  or  more  than  equal  to  the  total  capacity  of 
the  land  lines,  which  measure  287  miles  against  23 
miles  of  the  submarine, 

The    preparation    of    the    chemical    paper    for 
receiving  the  photographs  is  not  an  easy  matter, 


ELECTROLYTIC    RECEIVER  97 

as  one  must  have  a  paper  always  conductive, 
and  therefore  always  in  a  moist  condition,  and 
whilst  it  is  sufficiently  absorbent  it  must  have 
a  smooth  surface,  as  otherwise  the  grain  is  painfully 
prominent  when  the  picture  is  copied  for  reproduc- 
tion. The  resistance  of  the  paper  may  be  any- 
thing from  1,000  to  5,000  ohms,  and  as  it 
must  mark  instantaneously  with  a  current  of  about 
i  milliampere  it  requires  to  be  extremely  sensi- 
tive. The  speed  at  which  the  paper  passes  under 
the  stylus  is  3*75  inches  per  second,  and  since 
the  amount  of  the  element  liberated  which  causes 
the  discoloration  is  by  weight  equal  to  the  product 
of  current,  time,  and  electro -chemical  equivalent, 
it  is  seen  that  an  exceedingly  small  amount 
of  chemical  action  takes  place.  When  much  current 
is  lost  in  the  line  it  is  sometimes  necessary  to  in- 
crease the  voltage  at  the  sending  end.  Although 
only  about  a  milliampere  of  current  flows  actually 
through  the  paper,  twenty  or  thirty  may  flow 
through  the  line,  this  excess  of  course  going  into 
the  shunt  circuit  or  balancer  of  the  receiver.  The 
secondary  discharge  of  a  small  induction  coil  is 
quite  sufficient  to  mark  the  paper  used,  so  that  the 
effect  of  electrolysis  can  be  produced  with  prac- 
tically "  no  current,"  provided  the  tension  be 
sufficiently  high. 

The  first  experiments  were  made  with  the  telec- 
trograph  in  1909  at  the  Imperial  International 

P.T.  H 


98 


PHOTO-TELEGRAPHY 


Exhibition,  Shepherd's  Bush,  where  demonstra- 
tions were  given  about  eight  times  daily,  photo- 
graphs being  telegraphed  from  one  machine  to  the 
other  through  an  artificial  "  line  "  of  about  2,000 


FIG.  45. — Portrait  of  first  lady  councillor 
of  Liverpool.  Wired  by  the  Telectro- 
graph  from  Manchester  to  London. 

12  resistance;  the  machines  stood  some  16  or  20 
feet  apart,  so  that  both  sending  and  receiving 
operations  could  be  readily  observed  together. 

The  method  of  synchronising  was  practically  the 
same  as  that  described  for  the  telautograph,  except 


MANCHESTER    EXPERIMENTS          99 

in  so  far  as  the  receiving  machine  was  concerned. 
The  "  line  "  terminals  were  connected  to  the  spring 
tongues  of  the  reverser  (see  Chapter  III.),  which 
was  in  contact  with  two  upper  platinum  pins 
during  nearly  the  whole  revolution,  these  pins  lead- 
ing one  to  the  stylus  and  the  other  to  the  drum, 
i.e.,  the  back  of  the  sensitive  paper.  At  synchro- 
nism the  check  which  stopped  the  drum  revolving 
temporarily  automatically  lowered  the  tongues  into 
contact  with  two  other  pins  which  led  directly  to 
the  polarised  relay,  the  latter  switching  in  the 
mechanism  for  withdrawing  the  check. 

The  machines  worked  so  satisfactorily  over  the 
artificial  line  that  in  July,  1909,  I  was  tempted  to 
place  a  similar  instrument  in  Manchester,  where  an 
installation  of  Professor  Korn's  apparatus  was  in 
full  swing,  as  already  described.  The  first  expe- 
riments over  this  line,  some  200  miles  in  length, 
were  very  disappointing.  The  attempts  were  made 
with  line  sketches,  not  half-tone  photographs,  and 
the  lines  appeared  on  the  paper  as  so  many 
smudges  ;  each  mark  had  a  long  tail,  and  it  was 
evident  that  secondary  discharges  were  coming 
from  the  line  into  the  paper.  These  discharges 
were  much  more  noticeable  some  days  than  others . 

It  thus  became  obvious  that  the  capacity  and 
induction  effects  would  have  to  be  counterbalanced, 
and  after  a  series  of  experiments  the  means  already 
described  were  adopted,  with  what  success  has  been 

H  2 


IOO 


PHOTO-TELEGRAPHY 


seen  from  the  quality  of  the  pictures  telegraphed 
with  this  instrument  since  published  in  the  Daily 
Mirror . 

It  has  already  been  explained  that  a  graduation 
of  tone  in  a  photograph  is 
represented  in  a  line  half- 
tone photograph  by  lines 
becoming  gradually  nar- 
rower. This  tapering  down 
of  the  width  of  the  lines  in 
the  telegraphed  picture  re- 
ceived is  wonderfully  repro- 
duced, and  the  results  are 
therefore  truly  "photo- 
graphic " ;  indeed,  examined 
a  short  distance  away,  they 
are,  if  the  synchronisation 
has  been  good,  hardly  distin- 
guishable from  the  original 
photographs. 

In  October,  1909,  a  telec- 
trograph  was  installed  in 
Paris,  but  here  again  trouble 
was  at  first  experienced.  In  the  first  place,  the  line  is 
half  as  long  again  as  the  London-Manchester  line,  and 
in  the  second,  its  various  elements  are  distinctly  dif- 
ferent. The  first  picture  received  was  successful,  but 
then  the  line  conditions  must  have  changed,  because 
for  several  days  the  results  were  extremely  bad,  each 


FIG.  46. — Portrait  of  Mr. 
Howarth,  telegraphed 
from  Manchester  to 
London  by  the  Thome- 
Baker  Telectrograph. 


o 
a. 
ed 


LINE    PHOTOGRAPHS  101 

dot  running  into  next,  so  that  the  whole  surface 
of  the  paper  was  discoloured  and  all  the  details  of 
the  image  hopelessly  intermingled.  I  then  in- 
creased the  capacity  of  the  condenser  in  the  line 
balancer,  and  the  photographs  were  also  tempo- 
rarily made  with  a  coarse  line  screen  (30  to  the 
inch),  and  the  quality  was  at  once  better.  A  great 
deal  depends,  needless  to  say,  on  the  quality  of  the 
half-tone  photographs,  which  require  quite  a  par- 
ticular method. of  preparation. 

The  method  of  making  these  photographs  is  as 
follows  :  The  picture  to  be  telegraphed  is  pinned 
flat  to  a  board  or  placed  in  a  frame  with  glass 
over  it,  and  fixed  vertically  in  a  copying  apparatus. 
It  is  usually  illuminated  with  an  arc  lamp  at 
either  side  with  reflectors.  The  camera  used  for 
copying  it  has  a  half -tone  screen  fixed  at  a  certain 
distance  in  front  of  the  sensitive  plate.  This 
screen  consists  of  a  glass  plate  ruled  with  a  certain 
number  of  lines  to  the  inch  ;  thirty  or  thirty-five 
lines  to  the  inch  is  known  as  a  "  coarse  "  screen, 
the  number  for  high-class  illustrations,  printed  on 
surfaced  paper,  being  120  upwards  to  the  inch. 
Usually  two  such  screens  are  used,  crossed  so  that 
the  rulings  are  at  an  angle  of  90°  to  each  other,  and 
then  the  picture  is  broken  up  into  dots  ;  but  it  can 
easily  be  seen  that  where  the  picture  is  put  on  a 
cylinder  and  travels  round  beneath  a  tracing  point, 
lines  are  preferable  to  dots  ;  the  lines  of  course  lie 


102 


PHOTO-TELEGRAPHY 


along  the  length  of  the  cylinder,  so  that  the  tracer 
scrapes  over  them  and  not  along  them.  In  the  case 
of  dots  the  tracer  would  go  in  between  two  adjacent 
ones  very  often,  or,  as  its  path  is  at  a  slight  angle 


FIG.  47. — Half -tone  single  line  negative  image, 
as  ordinarily  used  for  the  Telectrograph. 

to  the  path  of  a  fixed  point  on  the  circumference 
of  the  cylinder,  it  would  occasionally  touch  two 
dots  in  consecutive  lines  at  once,  and  interfer- 
ence would  be  caused. 

The  single -line  screen  has  the  effect  of  breaking 


LINE    PHOTOGRAPHS  103 

up  the  picture  into  parallel  lines  which  vary  in  width 
according  to  the  density  of  the  photograph  at  each 
point.  Thus,  in  the  case  of  a  portrait,  the  dark 
coat  would  be  represented  by  wide  lines  close 
together,  a  light  part  of  the  face  by  fine  lines 
correspondingly  wide  apart,  the  distance  between 
the  centre  of  any  two  lines  being  always  constant. 
If  there  are  fifty  lines  per  inch,  no  line  can  be  wider 
than  5\j  inch ;  as  a  matter  of  fact,  it  should  not 
be  wider  than  -^  —  t,  where  t  is  the  width  of  the  point 
of  the  stylus,  otherwise  a  dark'  part  of  the  picture 
would  appear  in  the  telegraph  as  a  "  dead  black." 
The  print  from  the  half-tone  negative  is  now  pre- 
pared by  printing  from  it  (in  arc  light)  upon  a 
sheet  of  thick  lead  foil  coated  with  a  thin  layer  of 
fish-glue  rendered  sensitive  to  light  by  means  of 
a  soluble  bichromate.  When  printed  it  is  held 
under  a  tap,  and  all  the  unexposed  parts  dissolve 
away,  i.e.,  the  parts  in  between  the  lines.  The 
print  is  now  dried  and  placed  between  two  polished 
steel  plates,  and  put  into  a  press.  This  causes  the 
glue  image  to  sink  into  the  soft  metal  without  dis- 
torting it,  and  a  smooth  commutator  surface  is 
obtained,  which  therefore  offers  no  resistance  to 
the  stylus,  while  it  allows  of  very  intimate  con- 
tact between  the  stylus  and  the  picture. 

The  image  is  made  negative  for  the  telec- 
trograph,  as  wherever  there  is  bare  metal  a  black 
mark  is  produced  at  the  receiving  instrument.  The 


104 


PHOTO-TELEGRAPHY 


image  is  made  visible  by  staining  up  the  print  in 
an  aniline  dye  solution,  the  glue  taking  up  the 
colour  readily. 

Photo -engravers  know  that  in  making  a  half- 
tone photograph,  even  with  the  cross  screen,  a  good 
deal  of  the  detail  is  lost,  and  this  is  only  natural 
when  we  consider  that,  instead  of  a  solid  black  or 
grey,  we  have  only  dots  on  a  white  ground.  In 


FIG.  48. — Finish  of  the  St.  Leger,  wired  by  the  Telectrograph. 

making  a  single -line  picture  a  great  deal  more  is 
lost,  and  thus  before  making  the  screen  negative 
the  original  has  to  be  considerably  retouched,  the 
contours  have  to  be  very  clearly  defined  and  accen- 
tuated, and  the  paler  tints  have  to  be  made  con- 
siderably bolder,  as  these  lose  the  most  in  the 
reproduction.  The  solid  blacks,  on  the  other  hand, 
require  to  be  made  grey,  so  that  the  lines  repre- 
senting them  in  the  half -tone  picture  are  not  too 
wide  and  close  together. 


LINE    CAPACITY  105 

Future  progress  rests  so  much  on  greater  perfec- 
tion being  obtained  in  the  line  pictures  that  I  have 
dwelt  at  some  length  on  these  points.  The  present 
systems  are  good  and  practicable  ;  it  is  perfection 
of  detail  that  is  required.  M.  Chatenet  is  a  par- 
ticularly clever  photo -engraver,  and  has  rendered 
much  assistance  in  finding  the  best  means  of  the 
preparation  of  the  half-tone  pictures.  A  consider- 
able time  elapsed  at  Manchester  before  the  photo  - 
engravers  there  were  able  to  make  really  suit- 
able line  prints  ;  but,  having  once  found  out  the 
"  right  way/'  the  work  proceeds  quite  smoothly. 
But  what  I  would  like  to  point  out  is  that, 
although  telegraphed  pictures  are  now  to  be  seen 
so  regularly  in  the  Daily  Mirror  that  they  occa- 
sion no  surprise,  they  have  only  become  what 
they  are  through  the  attention  from  start  to  finish 
given  to  minute  details. 

By  means  of  the  apparatus  described  in 
Chapter  VI.  it  has  become  possible  to  make  a  great 
variety  of  experiments,  transmitting  pictures  over 
an  artificial  telephone  line  in  which  resistance,  self- 
induction,  leakance,  and  capacity  can  be  varied 
at  will.  By  examining  oscillographic  records  of 
these  transmissions,  various  arrangements  for  over- 
coming line  faults  can  be  tested,  and  their  practical 
utility  estimated.  The  problem,  of  photo -tele- 
graphy over  telephone  lines  is  closely  allied  in  many 
respects  to  ordinary  telephone  work,  only  that  the 


io6 


PHOTO-TELEGRAPHY 


electrical  impulses  are  of  far  longer  duration,  and 
represent  small  parts  of  a  picture  instead  of  vocal 
sounds. 

As    the    function    of    the    transmitting    instru- 
ment    is     merely    that     of    an     interrupter,     it    is 

clear  that  the   sending  bat- 
tery can  be  included  in  the 
receiving    station,    hence    a 
portable    apparatus    is    not 
impossible.    Portable  instru- 
ments are  now,  as  a  matter 
of    fact,    being    constructed, 
in  which  the  motive  power  is 
derived  from  a  particular  form 
of     clockwork     mechanism. 
The  portable  machine  is  the 
key  to    general    commercial 
utility,  and  its  developments 
will  be  watched  with  interest. 
One     drawback     to      the 
telectrograph,     viz.,    that    a 
negative    image    had    to    be 
used     on    the     transmitting 
cylinder  instead  of  a  positive  (the  latter  being  more 
easily    and    rapidly   prepared),    has    recently   been 
overcome.     A  positive  print  having  about  fifty  lines 
to  the  inch  is  used,  and  at  the  receiver  a  current  is 
passed  through  the  electrolytic  paper  which  con- 
tinuously discolours  it.      The  currents  transmitted 


FIG.  49. — M.  Riolle,  Public 
Prosecutor  in  the  Stein- 
heil  case ;  wired  from 
Paris  to  London  by  the 
Thome  -  Baker  Telec- 
trograph. 


DOUBLE    CURRENT    SYSTEM 


107 


from  the  sending  machine  are  of  opposite  direction 
to  this  continuous  current,  arid  neutralise  it.  Hence, 
whenever  the  stylus  of  the  transmitter  sends  a 
current  through  the  line  it  neutralises  the  con- 
tinuous current,  and  so  prevents  the  latter  from 
making  an  electrolytic  dot.  As  soon  as  the  trans- 
mitter current  has  ceased,  it  is  immediately  wiped 


FIG.  50. — News  photograph  wired  from  Manchester  to  London 
of  a  railway  accident  at  Stalybridge. 

out  by  the  continuous  current,  which  is  of  course 
shunted  on  to  the  telephone  line. 

The  use  of  a  double  current  system  in  telegraphy 
is  well  known,  and  greatly  increases  the  possible 
rate  of  working,  as  it  hastens  the  ordinarily  slow 
discharge  of  the  line.  It  thus  becomes  possible 
to  work  with  finer  screens  in  preparing  the  photo- 
graphs, and  to  obtain  a  correspondingly  greater 
amount  of  detail. 


CHAPTER    V. 

CONSIDERATIONS  OF  THE  TELEPHONE  AND 
TELEGRAPH  LINES  AND  THEIR  INFLUENCE 
ON  PHOTO-TELEGRAPHY. 

As  the  two  qualities,  leakance  and  resistance,  of 
the  lines  connecting  two  photo -telegraphic  instru- 
ments have  a  final  influence  on  the  limits  of  long- 
distance transmissions,  and  the  capacity  and  in- 
ductance factors  have  a  large  influence  on  the 
quality  of  the  pictures  and  the  rate,  etc.,  with  which 
they  can  be  transmitted,  some  short  discussion  of 
the  matter  becomes  necessary. 

The  actual  effect  of  capacity  is,  as  has  been 
pointed  out  elsewhere,  a  lengthening  of  the  dura- 
tion of  the  current,  but  we  shall  now  see  how  these 
effects  can  be  experimentally  demonstrated.  A 
modified  form  of  the  Einthoven,  or  string  galva- 
nometer, was  employed  to  record  photographically 
the  effects  of  capacity  on  the  currents  transmitted 
through  a  high -resistance  line  by  the  transmitter, 
as  used  in  the  telautograph  and  telectrograph.  The 
arrangement  is  seen  in  Fig.  51.  A  band  of 
sensitive  film  MOQ  travels  over  rollers  in  a  light- 
tight  box,  being  actuated  by  a  well  -  regulated 


OSCILLOGRAPH    RECORDER 


109 


clockwork  motor  ;  one  or  two  strings  (silver  wires 
Tcfeoth  inch  thick)  are  free  to  move  laterally  between 
the  tunnelled  poles  of  the  electro -magnet,,  and  a 
shutter  is  attached  to  them  where  the  optic  axis 
meets  them.  N  is  a  Nernst  lamp,  and  L  a  lens. 
The  lens  in  the  tube  T  throws  a  real  image  of  the 
shutter  over  the  horizontal  slit  S.  The  terminals 
A,  B  of  the  galvanometer  strings  are  connected  to 
the  metal  drum  and  stylus  of  a  photo -telegraphic 


MO' 


FIG.  51. 

transmitter,  across  which  capacity  can  be  shunted, 
or  inductance,  etc.,  can  be  placed  in  the  circuit. 

Every  time  the  stylus  of  the  transmitter  comes  in 
contact  with  the  metal,  current  flows  through  AB, 
which  is  laterally  displaced  ;  hence  the  shutter 
uncovers  the  slit  S  more  or  less  according  to  the 
current  strength.  A  series  of  images  of  the  slit  is 
thus  seen  on  the  moving  film  MOQ  on  develop- 
ment. The  elongation  and  widening  of  the  image 
due  to  capacity  can  be  seen  clearly  on  comparing 
the  two  records  shown  in  Figs.  52  and  53. 


no 


PHOTO-TELEGRAPHY 


a 

oj 
o 

o 

G 


>* 
'o 

03 

03 
0 


EFFECT   OF    MOMENTUM  in 

These  oscillographic  records  show  many  things 
of  great  interest .  Firstly,  that  if  the  metallic  space 
between  each  of  several  consecutive  glue  lines  in  a 
half-tone  print  be  s,  greater  than  that  si  between 
each  line  in  another  print,  the  current  passing 
through  the  strings  A,  B  is  greater  in  the  case  of 
the  s  lines  than  in  that  of  the  Si,  although  the  line 
resistance,  battery  power,  etc.,  be  the  same  in  both 
cases  ;  hence  a  definite  time  is  required  for  the 
current  transmitted  to  reach  a  maximum  value,  the 
possible  value  not  being  so  nearly  reached  when 
the  interruptions  are  very  rapid  as  when  slower,  and 
the  maximum  value  being  very  rarely  reached. 
Secondly,  that  where  a  large  number  of  consecutive 
currents  of  equal  period  p  are  transmitted,  the  dis- 
placement of  the  galvanometer  strings  increases 
gradually  to  a  maximum  value,  then  decreases,  and 
so  on,  instead  of  remaining  always  equal  and  pro- 
portional to  p.  Thirdly, -that  when  the  period  p 
has  a  certain  value,  equa.]  to  the  natural  period  of 
swing  of  the  strings,  the  displacement  is  excessive, 
and  very  much  higher  than  that  obtainable  under 
any  other  circumstances,  R  and  C  remaining  equal. 

The  effect  of  a  pumber  of  currents  of  equal  period 
to  cause  a  gradual  extension  of  the  swings  which 
reach  a  maximum  and  then  decrease,  indicates  that 
a  dead-beat  action  like  the  electrolytic  one  is  pre- 
ferable to  any  form  of  moving  part,  where  there 
is  definite  momentum,  and  kinetic  energy. 


112 


PHOTO-TELEGRAPHY 


The  overhead  wires  of  the  Paris -London  tele- 
phone line  are  600  Ibs.  copper  wire  in  France  and 
400  Ibs.  (per  mile)  in  England.  Their  capacities 
and  resistances  are  as  follows  : — 


Capacity  of 

Length  in 

Resistance 

each  wire 

miles. 

in  ohms. 

in  micro- 

farads. 

London  to  St.  Margaret's  Bay 

84-5 

183 

1-32 

St.  Margaret's  Bay  to  Sangatte 

23'0 

H3 

5'52 

(cable). 

Sangatte  to  Paris    . 

199-0 

294 

3'33 

Paris  (underground) 

4'8 

70 

o'43 

3H'3 

690 

io'6o 

The  total  capacity  is  thus  5*30  microfarads,  and  the 
resistance  1,380  li. 

In  the  lines  from  Manchester  to  London  there 
are  lines  of  different  weights,  from  300  Ibs.  to 
600  Ibs.  per  mile.  The  "  standard  cable  " 
employed  as  a  unit  consists  of  an  air-space  paper 
cable  with  a  loop  resistance  of  88  ohms  per  mile, 
and  an  average  mutual  electrostatic  capacity  of 
•054  microfarad  per  mile  between  wire  and  wire  of 
one  pair.  The  300  Ibs.  overhead  wire  may  be 
said  to  be  about  eleven  times  as  efficient  per  mile 
for  telephone  work  as  the  standard  cable,  the 
600  Ibs.  line  about  sixteen  times.  The  wire  to 
wire  capacity  of  the  overhead  lines  (300  Ibs.) 


CURRENT   ATTENUATION  113 

is  "00918  microfarad,  the  capacity  of  a  wire  to  earth 
'0153  per  mile. 

If  we  compare  a  mile  of  the  submarine  cable  with 
a  mile  of  the  overhead  as  above,  the  capacities  are 
roughly  as  0*24  to  '0245  ;  and  there  being  twenty- 
three  miles  of  cable  in  the  Paris -London  line,  it 
will  be  seen  that  the  difficulties  of  working  over 
it  are  considerably  greater  than  those  experienced 
in  our  own  country. 

In  the  case  of  an  alternating  current  passing 
through  the  lines,  there  is  a  definite  attenuation 
factor  according  to  Pupin  =  e~Pm,  where  e  is  the 
base  of  Naperian  logarithms,  /3  the  attenuation 
constant,  and  m  the  mileage.  /3  is  the  fraction  of 
the  current  at  any  moment  lost  in  the  passage  of  that 
current  through  a  mile  of  line.  The  current  em- 
ployed in  the  telectrograph  is,  as  already  ex- 
plained, of  a  character  somewhat  comparable  with 
an  alternating  current,  but  with  a  continuous  cur- 
rent impressed  on  it.  How  far  these  figures  are 
applicable  to  the  photo-telegraphic  work  remains 
to  be  found ;  the  contrary  current  used  in  the  telec- 
trograph is  especially  a  " wipe-out"  current,  and 
prevents  the  latter  part  of  each  cable  discharge. 

The  practical  effect  of  the  line  capacity  is  to 
lengthen  the  time  during  which  a  discharge  takes 
place  in  the  receiving  apparatus.  Thus  if  one  very 
brief  current  be  sent  through  a  high -capacity  line 
to  the  receiver — an  ideal  oscillograph  absolutely 

P.T.  I 


ii4  PHOTO-TELEGRAPHY 

dead  beat,  for  example — the  action  would  be 
longer  in  time  than  the  duration  of  closing  of  the 
circuit  at  the  transmitting  end. 

The  records  made  with  the  recording  apparatus 
already  described  show  that  when  currents  are 
transmitted  through  a  line  with  considerable  capa- 
city the  "  teeth  "  widen,,  and  are  inclined  one  to 
run  into  the  next.  This  effect  is  in  accordance  with 
the  results  obtained  on  the  telectrograph,  which 
forms  a  useful  and  very  sensitive  recording  appa- 
ratus in  itself.  When  a  series  of  short  contacts 
are  made  on  the  transmitter  these  should  produce 
short  marks  at  the  receiver,  but  the  actual  effect 
is  that  one  mark  runs  into  the  next. 

What  is  required,  then,  in  an  ideal  system  is  the 
shortening  up  of  these  elongated  impulses,  so  that 
the  effect  in  the  receiver  for  current  of  duration  t 
is  also  of  duration  t.  This  result  is  obtained  to  a 
very  fair  extent  in  the  balancer  already  described  in 
the  chapter  dealing  with  the  telectrograph. 

The  reader  may  possibly  have  thought  that  the 
introduction  of  the  above  matter  was  needless  in 
treating  the  subject  of  photo -telegraphy,  but  the 
leakance  of  long-distance  lines  and  their  capacity, 
and  the  attenuation  factor,  are  the  three  things 
which  chiefly  decide  the  question  :  How  far  and 
how  quickly  can  photographs  be  telegraphed  ? 

The  receiving  apparatus  destined  for  the  best 
work  between  two  places  A  and  B  is  usually  of  a 


DISTANCE    OF   TRANSMISSION        115 

different  character  from  that  suitable  for  two  other 
places  C  and  D.  In  extending  our  work  and  cover- 
ing very  great  distances  we  must  build  the  appa- 
ratus to  suit  the  conditions  under  which  it  is  to  be 
used . 


I  2 


CHAPTER    VI. 

THE  TELESTEREOGRAPH  OF  M.  BELIN— THE 
EARLY  WORK  OF  BELIN— CHANGES  IN  HIS 
SYSTEM— RECENT  EXPERIMENTS. 

ONE  of  the  most  indefatigable  workers  in  the 
field  of  photo -telegraphy  is  M.  Edouard  Belin,  who 
has  been  for  some  years  actively  engaged  in  work- 
ing out  a  system  of  his  own.  His  apparatus  has 
been  designated  the  telestereograph,  but  as  his 
method  of  transmission  has  quite  recently  under- 
gone a  radical  change,  it  will  be  better  to  describe 
his  first  successful  models  by  themselves. 

The  use  of  a  relief  photograph,  in  which  different 
tones  in  the  image  are  represented  by  different 
thicknesses  of  the  film,  to  vary  the  amount  of 
resistance  in  an  electric  circuit  containing  a  suit- 
able receiver,  has  been  referred  to  in  the  intrto- 
ductory  chapter,  and  the  idea  is  a  very  old  one. 
But  the  methods  employed  by  Belin,  both  in  the 
mechanism  for  varying  the  resistance  and  in  the 
means  of  reception,  were  very  ingenious,  and  he 
obtained  some  promising  results  over  artificial  lines 
and  loop  telephone  lines,  which  unfortunately  never 
seemed  to  surpass  a  definite  standard  attained  in 
1908. 


BELIN'S   TELESTEREOGRAPH         117 

A  photograph  in  relief  is  obtained  by  printing 
from  an  ordinary  negative  upon  what  is  termed 
carbon  tissue,  this  being  paper  coated  with  gelatine, 
which  is  rendered  sensitive  to  light  by  the  addition 
of  a  bichromate.  When  sufficiently  exposed,  the 
paper  is  "  developed  "  in  hot  water,  when  the 
gelatine  washes  away  from  the  unexposed  parts,  but 
remains  insoluble  where  there  has  been  much 
exposure  ;  moreover,  in  the  "  half-tones/'  the 
gelatine  washes  away  only  to  an  extent  depending 
on  the  amount  of  exposure,  I.e.,  on  the  density  of 


Shadow  Shadow  faint 

Middle  part 

tone 

FIG.  54. 

the  negative.  The  relief  picture,  if  we  were  to 
cut  a  fine  section  transversely  through  the  film, 
would  therefore  appear  as  shown  in  Fig.  54. 

Now  let  us  suppose  such  a  relief  picture  wrapped 
round  the  drum  DI  (Fig.  55)  of  Belin's  transmitter. 
This  is  a  heavy  metal  drum  turning  between  centres, 
the  whole  drum,  etc.,  moving  laterally  so  that  a 
stylus  fixed  at  S  traces  a  spiral  path  over  the  photo- 
graph. Now  this  stylus  consists  in  reality  of  a 
sapphire  or  a  hardened  steel  point  fitted  to  the  end 
of  a  rod  attached  to  a  long  arm  movable  about  F, 
the  fulcrum.  The  diagram  is  not  flrawn  to  scale, 
S  being  actually  close  to  the  fulcrum.  When  a 


n8 


PHOTO-TELEGRAPHY 


high  relief  in  the  photograph  happens  to  be  at  the 
point  S  the  stylus  is  pressed  outwards  an  amount  d, 
so  that  the  small  platinum  wheel  W  fixed  at  the  end 
of  this  arm  is  displaced  an  amount  d  X  M,  if  the 
distance  from  F  to  R  be  M  times  as  great  as  that 
from  S  to  F. 

The  movement  to  and  fro  of  this  little  wheel  is 
therefore  always  in  accordance  with  the  relief  of 


FIG.  55. 

the  photograph.  It  travels  over  a  very  small 
rheostat,  consisting  of  several  coils  of  different 
resistances,  one  end  of  each  coil  being  soldered  to 
a  thin  copper  plate,  the  other  end  to  one  unit  of 
the  telephone  line.  These  copper  strips  arc  each 
separated  by  a  narrow  strip  of  insulating  material, 
and  the  top  surface  worked  dead  flat,  so  that  the 
wheel  W  travels  backwards  and  forwards  over 
them  ;  the  surface  of  this  rheostat  should  in  reality 


BELIN'S    RECEIVER  119 

lie  along  the  circumference  of  a  circle  whose  centre 
is  F  and  radius  FW. 

The  top  of  the  metal  arm  FR  is  joined  to  the 
other  wire  of  the  telephone  line  ;  the  function  of 
the  Belin  transmitter  is  thus  to  send  into  the  line 
a  practically  continuous  current  which  varies  in 
intensity  owing  to  the  wheel  W  being  in  contact 
with  a  resistance  coil  whose  resistance  is  in  accord 
with  the  amount  of  relief  at  each  instant  at  the 
stylus  S. 

This  varying  current  (continuous  because  the 
rheostat  strips  are  so  close  together  that  the  wheel 
is  always  in  contact  with  two  or  more  adjacent 
strips)  is  utilised  at  the  receiving  station  to  form 
a  photographic  image. 

For  this  purpose  Belin  employs  an  oscillograph 
of  the  Blondel  pattern,  which  consists  of  two  fine 
wires  stretched  across  the  field  of  a  fairly  powerful 
electro -magnet.  The  current  passes  down  one 
string  and  up  the  other,  not  through  both  in  the 
same  direction  as  in  the  case  of  Korn's  string 
shutter  galvanometer  ;  hence,  owing  to  the  torque 
produced,  the  wires  (AB  in  the  figure)  twist  the 
small  mirror  M  attached  to  them  at  the  centre. 

To  make  the  damping  factor  e~kt  as  great 
as  possible,  the  moving  part  works  in  oil,  but 
though  this  damps  down  the  vibrations  set  up  owing 
to  the  inflow  of  a  sudden  current,  it^must  necessarily 
reduce  the  sensitiveness.  This  reduced  sensi- 


120  PHOTO-TELEGRAPHY 

tiveness  is  not  of  great  consequence,  because  the 
change  in  intensity  of  the  current  is  not  very  rapid 
nor  periodic  as  it  is  in  the  case  of  the  transmis- 
sion of  a  single-line  half-tone  photograph.  But  it 
renders  the  obtaining  of  very  fine  details  uncer- 
tain, one  merging  into  the  other  or  being  lost 
altogether.  It  is  of  course  possible  to  increase  the 
sensitiveness  of  the  galvanometer  by  using  a  more 
powerful  magnetic  field,  and  by  using  longer  wires, 
but  where  oil  is  used  in  the  latter  case  there  would 
be  more  friction  owing  to  increased  field  of  sur- 
face tension,  and  I  think  that  eventually  M.  Belin 
will  be  obliged  to  utilise  the  methods  of  damping 
the  vibrations  that  have  been  applied  to  the  string 
galvanometer  in  place  of  oil. 

Now  let  us  see  how  the  photographic  image  is 
formed.  A  Nernst  lamp  N  (Fig.  55)  is  placed 
at  such  a  position  that  a  pencil  of  light  con- 
centrated from  it  upon  the  mirror  M  is  reflected 
upon  a  diaphragm  G.  This  diaphragm  has  a 
rectangular  aperture,  so  that  the  light  reflected 
from  M  on  to  it  when  M  is  in  the  zero  position 
falls  upon  one  end  of  the  aperture ;  as  the  mirror 
swings  to  one  side,  so  the  light  falls  more  towards 
the  other  end  of  the  aperture,  etc.  Now  this 
aperture,  which  had  much  better  have  been  a 
triangular  one  as  Korn  uses  in  his  selenium 
machines,  is  covered  with  a  graduated  sheet  of 
glass,  which  Belin  terms  his  "  scale  of  tints."  It 


PRACTICAL   EXPERIMENTS  121 

is  merely  a  photographic  negative  having  practi- 
cally no  silver  deposition  at  one  end  of  the  rect- 
angle, and  graduating  to  a  dense  deposit  at  the 
other  end.  As  the  mirror  swings  to  one  side, 
so  the  light  from  it  falls  on  a  denser  portion 
of  the  scale  of  tints,  and  less  light  emerges  from 
the  glass. 

Behind  the  diaphragm  is  a  condenser  C,  which 
refracts  the  collected  light  and  brings  it  to  a  point 
on  the  drum  D%,  round  which  a  sensitive  film  is 
wrapped.  The  intensity  of  this  spot  of  light  is 
proportional  to  the  current,  hence  inversely  to  the 
relief  in  the  photograph.  The  drum  D2  travels 
sideways  as  it  revolves,  the  pitch  of  thread  used 
being  the  same  as  that  in  the  transmitter.  It 
travels  in  a  light-tight  box  fitted  with  a  tube  and 
diaphragm,  as  in  the  case  of  the  telautograph.  But 
M.  Belin  has  happily  arranged  that  the  one 
cylinder  serves  both  as  transmitter  and  receiver. 

In  1907  and  1908  Belin  made  various  experi- 
ments over  a  long-distance  telephone  line,  with  the 
two  apparatus  in  one  room  under  observation. 
Thus  he  had  two  lines  between  Paris  and  Lyons 
linked  up  at  Lyons,  the  two  machines  being  at  Paris, 
and  the  current  had  therefore  to  travel  to  Lyons  and 
back  while  passing  from  the  transmitter  to  the 
receiver. 

His  method  of  synchronising  differs  little  from 
that  already  described,  but  in  the  most  recent 


122  PHOTO-TELEGRAPHY 

models  he  has  arranged  that  the  cylinders  may  be 
driven  at  one  of  three  different  speeds,  so  that  the 
transmission  can  be  effected  rapidly  or  slowly  as 
desired.  This  is  a  very  useful  feature  for  experi- 
mental instruments. 

The  method  of  employing  a  rheostat  and  travel- 
ling wheel  has  now  been  more  or  less  abandoned, 
and  he  has  adapted  to  the  instruments  a  special 
form  of  microphone,  which  has  given  some  remark- 
ably good  results  over  artificial  lines,  I.e.,  under 
laboratory  conditions. 

It  is  of  course  well  known  that  if  a  diaphragm  of 
iron  be  fixed  near  the  poles  of  a  magnet,  the  mag- 
netic lines  of  force  pass  through  the  diaphragm. 
If  the  diaphragm  be  brought  nearer  to  or  further 
from  the  poles,  a  change  in  the  magnetic  field  takes 
place.  If  small  coils  be  wound  round  the  pole- 
pieces  and  connected  in  series  with  each  other  and 
with  a  battery  and  telephone,  then  any  shift  in  the 
position  of  the  diaphragm  will  be  noticed  by  a 
sound  in  the  telephone.  Belin  conceived  the  idea 
of  making  the  stylus  press  against  the  diaphragm 
of  the  microphone,  so  that  the  pressure  on  it  would 
vary  in  accordance  with  the  relief  in  the  photo- 
graphic image  ;  this  would  vary  the  magnetic  field 
and  so  change  the  power  of  a  current  of  electricity 
passed  through  the  microphone  in  series  with  a 
battery  and  the  two  wires  of  the  Blondel 
oscillograph. 


MICROPHONE    TRANSMITTER        123 

It  will  at  once  be  seen  that  in  this  procedure  we 
are  dealing  with  currents  of  very  low  magnitudes, 
and  Belin  found  that  considerable  modification  of 
his  apparatus  was  necessary.  In  the  first  place  the 
relief  in  the  photographs  as  used  for  his  original 
machines  was  much  too  great,  and  whereas  very 
thickly -coated  tissue — difficult  to  print  and  slow  to 
dry — had  been  at  first  used,  he  now  uses  very  thin 
tissue,  so  that  the  different  thicknesses  of  gelatine 
which  correspond  to  different  tones  are  very  minute. 
If  we  take  the  curve  showing  the  relation  between 
the  distance  of  the  microphone  diaphragm  from  the 
magnet  poles  and  the  current  strength  at  the 
receiver,  it  is  found  that  only  a  short  portion  of 
such  curve  is  suitable  for  the  system,  and  much 
variation  (and  hence  much  thickness  of  film)  is 
impossible  in  the  position  of  his  diaphragm.  The 
microphone  used  is  a  large  form  of  carbon  instru- 
ment, in  which  the  pressure  of  the  diaphragm  on 
three  carbon  balls  varies  their  resistance,  and 
therefore  the  strength  of  the  current  flowing 
through  the  circuit.  With  a  large  instrument  of 
this  type  he  can  allow  of  much  greater  variation  in 
the  position  of  the  diaphragm  than  is  usual  in  the 
diaphragm  of  an  ordinary  telephone  ;  the  latter, 
measured  at  the  centre,  being  something  like  io~6 
cm.  for  a  just  audible  sound. 

By  making  use  of  a  bridge  arrangement,  the 
balance  of  which  is  upset  by  the  alteration  in  resist- 


I24 


PHOTO-TELEGRAPHY 


ance  of  the  carbon  balls,  Belin  proposes  to  telegraph 
pictures  over  long  distances  with  his  modified  appa- 
ratus, using  a  Blondel  oscillograph  of  heavier  type 
as  regards  field  magnets,  and  a  lighter  suspension 
for  the  mirror.  This  could  be  turned  through  a 
greater  angle  for  a  given  current  if  the  wires  to 


FIG.  56. — Photograph  transmitted  by  M.  Belin's  Telestereo- 
graph,  over  an  artificial  line. 


which  it  was  attached  were  increased  in  length  and 
their  tension  lessened,  but  the  period  of  swing 
would  be  greater. 

M.  Belin  has  obtained  some  good  results  with 
his  system,  an  example  of  which  Is  shown  in 
Fig.  56.  The  results  are,  however,  characterised 
by  a  soft  diffused  appearance,  which  is  not  always- 


TRANSMITTING    LINE    SKETCHES    125 

a  disadvantage.  For  the  telegraphy  of  line  draw- 
ings/ pen-and-ink  sketches,  etc.,  he  employs  a 
much  simpler  arrangement  than  the  microphone, 
a  diagram  of  which  is  given  in  Fig.  57.  A 
metal  arm  FM  is  placed  so  that  it  can  turn 
about  F,  and  it  has  a  stylus  S  that  presses  lightly 
against  the  transmitting  drum.  The  line  pic- 
ture is  prepared  by  the  carbon  process,  and  each 
line  is  in  high  relief.  When  a  line  comes  into  con- 


FIG.  57. 

tact  with  the  stylus  the  arm  FM  is  pushed  out- 
wards, and  the  two  platinums  /?,  p  are  thrown  out 
of  contact.  This  breaks  the  electric  circuit,  and 
current  no  longer  flows  into  the  line  to  the  re- 
ceiver. It  is  claimed  that  this  method  is  particularly 
suitable  for  the  transmission  of  writing  or  printed 
matter,  and  might  prove  of  value  for  international 
banking  purposes,  etc.  Such  a  transmitter  is  of 
course  only  an  alternative  to  the  Casselli  trans- 
mitter, as  used  in  the  Korn  telautograph  and  the 


126  PHOTO-TELEGRAPHY 

author's  telectrograph,  and  is  not  so  practical,  since 
the  figure  of  merit  of  the  contact  breaker  would 
require  to  be  very  high  indeed  to  enable  it  to 
compete  with  the  metal  stylus  tracing  over  a 
flush  surface. 

The  synchronising  arrangements,  motors,  etc., 
used  in  the  telestereograph  are  so  similar  to  those 
already  described  that  any  further  reference  to  them 
is  unnecessary.  It  may  be  said  in  conclusion,  how- 
ever, that  M.  Belin  has  found  one  solution  to  the 
problem  of  photo -telegraphy  which  may  prove 
important  when  further  matured. 


CHAPTER   VII. 

THE    TRANSMISSION    OF    PHOTOGRAPHS    AND 
PICTURES  BY  WIRELESS  TELEGRAPHY. 

ANY  attempt  to  solve  the  somewhat  delicate 
problem  of  transmitting  photographs  by  "  wire- 
less "may  at  first  sight  seem  unnecessary.  But  it 
remains  to  be  seen  whether,  for  long-distance  work, 
it  will  not  prove  both  more  rapid  and  less  expensive 
than  transmission  by  cable,  especially  where  much 
water  intervenes  as  between  America  and  Ireland 
or  this  country.  As  seen  in  Chapter  V.,  the 
capacity  of  underground  cables  is  very  great  as 
compared  with  ordinary  overhead  wires,  besides 
which,  between  America  and  England,  either  two 
cables  would  be  required,  or  one  and  an  earth 
"  return."  The  former  would  be  extremely  costly, 
and  the  latter  would  render  necessary  apparatus 
of  a  very  delicate  and  sensitive  character. 

The  prospects  opened  up  by  a  wireless  method 
of  transmission  are,  on  the  other  hand,  of  an 
encouraging  nature,  as  not  only  could  long  dis- 
tances be  covered  at  a  high  spaed,  but  photo- 
graphs of  criminals  could  be  telegraphed  to  ships 


128  PHOTO-TELEGRAPHY 

fitted  with  a  receiving  apparatus,  and  sketches  or 
plans  could  be  transmitted  between  different 
sections  of  an  army. 

Mr.  Hans  Knudsen  was  the  first  to  demonstrate 
a  wireless  apparatus,  and  I  have  since  effected 
satisfactory  transmissions  by  two  new  methods, 
which  would  be  possible  in  actual  practice  over 
considerable  distances,  the  latter  method  when 
developed  being,  in  the  opinion  of  some  of  our 
best  wireless  experts,  capable  of  working  across 
the  Atlantic.  The  scheme  of  Knudsen  would 
not,  in  my  opinion,  be  practicable  over  any  dis- 
tance, for  reasons  that  have  been  made  clear  by 
experiments  carried  out  in  my  own  wireless  work. 

Knudsen  employed  a  flat  plate  on  which  a  sketch 
in  raised  lines  or  a  photograph  in  which  the  dark 
parts  were  resolved  into  lines  in  relief  was  placed. 
This  travelled  up  under  a  style  and  back  again,  each 
upward  travel  being  a  fraction  of  an  inch  to  the  side 
of  the  previous  one.  A  metal  stylus  was  fixed  over 
the  flat  plate,  and  this,  by  grazing  against  the  raised 
parts  of  the  picture,  interrupted  the  primary  of  an 
induction  coil,  whose  secondary  was  arranged  with 
a  spark  gap.  A  coherer  was  used  as  the  detector, 
and  this  was  continuously  decohered  by  a  striker 
driven  at  a  high  speed  by  means  of  a  small  electro- 
motor ;  the  coherer  actuated  a  relay  which  caused 
a  pointed  metal  stylus  to  dig  into  the  surface  of 
a  glass  plate  coated  with  lampblack  •  an  image  of 


KNUDSEN'S   APPARATUS  129 

scratches  was  thus  produced,,  which  could  be  printed 
from  like  an  ordinary  photographic  negative. 

The  synchronising  was  effected  by  the  smoked 
glass  plate  throwing  out  the  stylus  circuit  at  each 
end  of  its  travel  and  switching  in  another  circuit 
which  released  it  and  set  it  free  to  travel  again. 
The  results  were  crude  and  streaky  in  appearance. 

Mr.  Knudsen  gave  some  demonstrations  in  1909 
at  the  Hotel  Cecil,  and  transmitted  a  picture  of 
the  King,  by  his  wireless  machines,  across  the 
room  in  which  the  apparatus  was  displayed. 

Like  most  workers  who  begin  their  wireless 
studies  on  a  modest  scale,  I  used  a  coherer  in  the 
early  experiments  in  order  to  detect  the  signals 
transmitted  from  the  sending  apparatus.  These 
signals  are  of  course  regulated  by  the  lines  or  dots 
of  which  the  photographic  image  is  composed,  and 
the  lines  in  a  line  drawing  or  half-tone  photograph 
really  act  as  the  interruptors  of  the  primary  circuit. 

It  will  be  more  convenient  to  describe  briefly  one 
or  two  of  the  ordinary  methods  of  wireless  tele- 
graphy, as  the  description  of  the  photo -telegraphic 
apparatus  will  then  be  clearer  to  those  whose  work 
does  not  carry  them  into  the  "  realm  of  wireless." 

If  we  take  an  induction  coil  as  shown  in  Fig.  58 
and  apply  a  suitable  battery  to  the  primary  winding, 
the  current  of  which  can  be  rapidly  interrupted  by 
means  of  an  interrupter  I,  a  spark  will  pass  between 
the  terminals  P,  P  of  the  secondary  coil.  If  now  we 
P.T.  K 


130 


PHOTO-TELEGRAPHY 


shunt  these  with  a  capacity  K  and  an  inductance  X, 
and  bring  the  spark  balls  P,  P  hear  together,  the 
spark  becomes  very  intense,  and  electrical  oscilla- 
tions are  set  up,  the  frequency  of  which  is  given  by 
the  expression 


n  = 


where  n  is  the  frequency  and   L  is  the  inductance 


FIG.  58. 

measured    in    centimetres,  and    C   the   capacity   in 
microfarads. 

If  now  we  use  the  inductance  X  as  the  primary  of 
a  small  transformer,  and  the  secondary  Y  is  placed 
between  a  connection  to  earth  E  and  the  aerial  wire 
or  wires  of  the  antenna  A,  and  the  oscillation  fre- 
quency of  the  aerial  circuit  tuned  to  that  of  the 
spark  gap  circuit,  we  have  a  transmitting  station 


WIRELESS   SIGNALS  131 

suitable  for  sending  signals  by  wireless.  If  the 
current  applied  to  the  primary  of  the  coil  B  can  be 
interrupted  by  a  Morse  key,  then  by  tapping  for 
long  and  short  periods  we  send  out  trains  of  damped 
waves  for  long  and  short  periods  respectively, 
which  correspond  to  the  dashes  and  dots  used  in 
the  Morse  code. 

Now  in  wireless  photo -telegraphy  our  trans- 
mitting machine  clearly  takes  the  part  of  the 
Morse  key,  and  just  as  a  sentence  of  words  and 
letters  can  be  made  up  of  dots  and  dashes,  so  a 
photographic  image  is  constructed  of  long  or 
short  marks  in  proper  sequence  on  the  receiving 
drum  of  the  telectro  graph. 

In  a  simple  receiving  circuit  we  have  the  aerial 
antenna  A  and  earth  plate  E  connected  with  the 
ends  of  a  coil  X  placed  close  to  another  coil  Y  of 
very  fine  wire,  which  latter  transmits  the  wireless 
"  oscillation  "  through  a  condenser  K  into  the  co- 
herer C.  A  battery  B  and  relay  R  are  also  in  series 
with  the  coherer,  which  becomes  conductive  when 
the  aerial  receives  an  electro-magnetic-wave.  The 
relay  is  thus  actuated,  and,  by  means  of  a  local 
circuit  closed  by  it,  a  small  electro  -  magnetic 
hammer  is  made  to  tap  the  coherer,  which  then 
becomes  non -conductive  again,  so  that  the  relay 

contact  is  unmade. 

t» 

An  ordinary  form  of  coherer  is  an  exhausted 
glass  tube,  in  the  centre  of  which  are  two  silver 

K  2 


132 


PHOTO-TELEGRAPHY 


plugs  near  together,  a  part  of  the  intermediate 
space  being  filled  with  silver  and  nickel  filings. 
When  a  current  is  received  these  filings  cohere  and 
make  tolerable  contact,  so  that  the  wires  connected 
to  the  silver  plugs  will  convey  a  current.  The  co- 
hesion requires  then  to  be  destroyed  by  a  tap  or 
knock,  when  the  coherer  again  becomes  a  sensitive 


FIG.  59.  —Diagram  of  Marconi's  Electromagnetic 
Detector. 

detector.  A  far  more  satisfactory  arrangement 
devised  by  Marconi  for  detecting  the  signals  is  seen 
in  Fig.  59.  Here  a  string  made  of  fine  soft-iron 
wires  travels  round  two  discs  D,  D,  which  are 
actuated  by  clockwork.  A  glass  tube  fits  over  a 
small  portion  of  the  travelling  wire,  round  which  is 
wound  a  fine  wire  coil,  the  ends  of  this  coil  being 
connected  to  the  antenna  and  earth  plate  respec- 
tively. A  small  secondary  coil  S  wound  over  the 


FIRST   APPARATUS 


133 


primary  S  goes  to  a  sensitive  telephone  T.  Two 
horseshoe  magnets  are  placed  as  shown  in  the 
diagram,  with  similar  poles  together,  and  as  the 
wire  string  travels  past  them  the  magnetism  induced 
is  retained  by  hysteresis,  this  being  immediately 
destroyed  by  the  passing  of  the  wireless  oscilla- 
tions through  P,  the  magnetism  shifting  back 


FIG.  60. — Arrangement  first  used  by  the  Author  for  the 
wireless  transmission  of  pictures. 

again  to  the  normal  position.  This  change  of  the 
induced  magnetism  with  respect  to  the  magnets 
causes  a  sound  in  the  telephone,  which  is  suffi- 
ciently sensitive  to  respond  to  currents  of  io~13  ampere 
and  less. 

The  first  wireless  pictures  transmitted  with  any 
success — and  I  am  speaking  of  success  from  an 
experimental  point  of  view — were  obtained  with  the 


i34  PHOTO-TELEGRAPHY 

apparatus  shown  diagrammatically  in  Fig.  60. 
The  left-hand  side  shows  the  transmitter,  the  right 
the  receiving  arrangement. 

D  is  the  drum  of  a  telectrograph  as  described  in 
Chapter  IV.,  the  stylus  tracing  over  a  sketch  drawn 
in  insulating  ink  on  a  sheet  of  lead  foil  ;  D  and 
the  style  had  a  condenser  shunted  across  to  prevent 
sparking.  The  current  from  the  battery  A  was 
interrupted  by  the  lines  of  the  picture,  the  mag- 
netism in  M  being  thus  intermittent.  The  relay  at 
M  broke  the  contact  of  the  battery  B  in  circuit  with 
the  primary  P  of  an  induction  coil,  S  being  the 
secondary,  electrical  oscillations  being  set  up  in  the 
manner  already  described. 

A  negative  print  was  used  on  the  drum  D,  so  that 
sparking  between  the  balls  took  place  only  when  a 
"  line  "  in  the  picture  was  in  contact  with  the  stylus. 
The  capacity  K  and  inductance  J  in  the  oscillatory 
circuit  could  be  adjusted,  and  for  long  distances 
the  aerial  and  earth  would  be  connected  inductively. 

A  short  wave  of  about  40  metres  was  em- 
ployed, this  being  determined  by  the  expression 

-  =     ,  )    where  v  =  3  X  io10  cm. 

*  v  capacity  inductance 

=  the  velocity  of  electro-magnetic  oscillations,  and 
A  is  the  wave-length. 

Turning  now  to  the  receiving  circuit  the  aerial 

and    earth    were    connected   to   the    primary   of   a 

'  jigger,"  the  current  being  transformed  down  by 


FIRST   EXPERIMENTS 


135 


the  secondary,  and  passed  through  the  coherer  with 
a  condenser  K   in  series.    A  rather  insensitive  relay 


FIG.  61. — Sketch  of  head  and  shoulders  of  a 
lady.     Transmitted  by  wireless. 

of  the  telephone  service  pattern  was  inserted  in  the 
coherer -battery  circuit,  the  battery  consisting  of 
two  dry  cells.  The  local  circuit  of  this  relay 
actuated  a  second  relay  through  another  battery  of 


136 


PHOTO-TELEGRAPHY 


two  dry  cells,  and  the  local  circuit  of  this  second 
relay  included  the  receiving  circuit  of  the  telec- 
trograph,  as  shown  in  the  diagram. 

The  use  of  a  contrary  current  running  through 
the  receiver  was  necessary  to  render  the  marks  clear 
and  short. 

A  local  shunt  circuit  was  also  used  from  the  first 
relay  to  actuate  the  decoherer,  which  consisted  of  a 


To  Aerial 


To  Earth 


FIG.  62. 


very  lightly  built  electro -magnetic  striker  which 
tapped  the  coherer.  This  decohesion  was  later 
effected  in  a  much  simpler  manner,  the  act  of 
striking  the  coherer  closing  a  local  circuit  which 
produced  an  electrolytic  mark  on  the  paper  of 
the  receiving  drum. 

In    the    figure,,    EE    is   an   electro -magnet,    the 
windings   in   series   with   the  battery   Y,   and  the 


COHERERS 


137 


local  side  of  the  relay  R.  The  coherer  AB  was 
fixed  in  rigid  supports,,  and  to  one  end  was  attached 
a  fixed  brass  collar  fitted  with  a  platinum  pin  P, 
the  magnet  armature  MN  consisted  of  a  piece  of 
iron  tape  fitted  to  an  aluminium  rod  ending  in  a 
piece  of  spring  brass  fixed  to  the  pillar  K.  The 
striker  was  fitted  to  the  end  of  this  light  rod  and 
when  it  struck,  the  force  of  the  blow  was  taken  off 
owing  to  its  ability  to  work  back  through  a  hole 
in  the  rod,  the  spring  Q  keeping  it  normally 
in  a  fixed  position.  When  the  platinum  pins 
touched,  the  force  of  impact  decohered  the  coherer, 
and  also  completed  the  circuit  of  the  electrolytic 
receiver.  In  this  way  I  was  able  to  get  a  very 
precise  movement,  in  which  one  short  wave  train 
caused  one  tap  ;  hence  one  mark  was  made  on  the 
telectrograph  paper  for  one  dot  or  "  contact  "  in 
the  transmitter. 

The  "  stickiness  "  of  coherers,  however,  renders 
good  synchronising  difficult,  and  a  straight  line 
would  always  appear  somewhat  wavy  in  the  re- 
ceived picture.  Moreover,  if  the  apparatus  were 
working  with  certainty,  rapidity  was  impossible, 
and  after  making  various  interesting  records,  the 
work  was  continued  on  other  lines.  • 

I  will  now  proceed  to  describe  the  most  recent 
wireless  methods  which  promise  to  give  more  satis- 
factory results,  especially  as  original  experiments 
make  it  probable  that  half-tone  photographs  will 


138 


PHOTO-TELEGRAPHY 


be  transmitted  at  a  considerable  speed  with    the 
apparatus.* 

The  transmitting  apparatus  consists,  as  before, 
of  a  metal  drum  revolving  under  a  stylus,  a  metal 
foil  print,  the  image  of  which  consists  of  glue  or 
shellac  lines,  being  wrapped  round  it.  The  battery 


FIG.  63. — Quartz  string  and  selenium  cell  arranged  for 
receiving  and  transforming  up  electrical  oscillations. 

current  flows  through  the  cylinder,  picture,  and 
stylus  to  a  very  lightly-built  relay  capable  of  work- 
ing at  a  high  speed  ;  this  relay  in  turn  actuates  a 
heavier  one  which  causes  the  interruptions  in  the 
primary  of  the  alternator  or  induction  coil.  If  a 
coil  be  used,  a  turbine  or  other  mercury  brake  is 
essential. 


Prov,  Patent  361/10, 


A    RECENT    RECEIVER 


139 


The  oscillations  are  transformed  at  the  receiving 
station  and  the  secondary  of  the  transformer  is 
connected  to  a  valve  receiver  (Marconi),  this  in 
turn  being  connected  with  a  battery  E  and  the 


FIG.  64. — Sketch  of  the  King 
transmitted  by  the  Author's 
wireless  apparatus. 

string  AB  of  a  large  galvanometer.  The  construc- 
tion of  the  galvanometer  is  somewhat  similar  to  that 
of  Korn's  modification  of  the  Einthoven  instrument, 
already  described  at  some  length.  The  "  string  " 
AB  is  in  this  case,  however,  a  qua?tz  fibre,  silvered, 
about  i^Jooth  inch  in  diameter.  It  is  free  to  move 


140  PHOTO-TELEGRAPHY 

laterally  in  a  very  powerful  magnetic  field,  and  a 
current  of  io~8  amperes  will  displace  it  to  a  con- 
siderable extent. 

Light  from  a  powerful  but  steady  arc  L  passes 
through  the  condensing  lens  C  so  as  to  form  a 
shadow  of  the  wire  AB  upon  a  fine  metal  slit  H. 
When  a  current  passes  through  the  wire  and  causes 
it  to  shift,  the  slit  is  uncovered,  and  light  passes 
through  and  illuminates  a  very  sensitive  selenium 
cell  SS.  A  weak  current  passes  through  this  cell 
from  the  battery  EI  into  a  sensitive  relay  R,  which 
also  has  a  high  speed  of  working.  When  the  sele- 
nium cell  is  feebly  illuminated,  its  resistance  drops, 
and  the  current  is  sufficiently  increased  to  actuate 
the  relay.  The  local  circuit  of  the  relay  includes  a 
battery  of  about  20  volts  and  the  telectrograph 
receiver  O,  a  contrary  current  being  passed  through  a 
resistance  into  it  also,  as  a  shunt  in  the  manner 
indicated  in  the  diagram. 

As  the  image  is  visible,  being  received  by  the 
electrolytic  method,  it  is  not  necessary  to  have  any 
synchronising  gear  on  the  receiver.  A  datum  line 
is  drawn  right  across  the  picture  being  transmitted, 
and  near  the  commencement.  The  reproduction  of 
this  line  is  carefully  watched  during  the  reception, 
and  the  line  is  made  to  lie  close  against  a  line 
drawn  across  the  electrolytic  paper.  If  the  line 
being  received  diverges  from  the  drawn  line  then  it 
is  known  that  the  receiving  drum  is  travelling  either 


A    RECENT    RECEIVER.  141 

too  quickly  or  too  slowly,  and  the  motor  is  regulated 
accordingly. 

It  will  be  seen  that  the  wireless  transmission  of 
pictures  requires  both  delicate  adjustment,  and 
accurately -built  driving  machinery.  We  are 
depending  on  a  movement  of  about  the  five-thou- 
sandth part  of  an  inch  for  our  recording,  and  there 
are  a  number  of  pieces  of  delicate  apparatus,  all 
reciprocative,  which  require  to-  be  in  perfect 
harmony. 

In  all  such  work  as  this  results  can  only  be 
obtained  slowly,  and  progress  is  often  only  apparent 
to  those  actually  in  touch  with  it.  Time  alone  will 
show  to  what  extent  wireless  photo -telegraphy  will 
be  of  value. 


INDEX 


A. 

ADJUSTMENTS  of  telectrograph, 

94 
Advantages  of  photo-telegraphy, 

75 

Alphabet   system    of    transmis- 
sion, 2 

Amstutz,  4,  8 

Aperture,  triangular  of  receiver, 

37 

Artificial  line,  105 
Attenuation  constant,  113 
Ayrton,  105 

B. 

BAIN'S,  chemical  telegraph,  20 
Bakewell,  2,  88 
Balancing  of  line,  92,  96 
Baudot  induction,  54 
Belin,  M.  Edouard,  116 
Belin's  transmitter,  117 

for  line  drawings,  125 
s  with  microphone,  122 
Berjeanneau,  14 
Berlin,  experiments  with,  48 
Bernochi,  wireless  apparatus,  14 
Bidwell,  Shelford,  4 
Blondel,  119 

c, 

CAPACITY,  effects  of,  95,  96,  108. 

H3 
wire  to  earth,  113 


Carpentier,  M.  J.,  49 

Caselli,  12 

Caselli's  pan-telegraph,  10 

stylus,  89 

transmitter,  61 
Charbonelle,  12,  14 
Chatenet,  19,  49,  76 
Chemical  receiving  paper,  96 
Condenser,  in  line  balancer,  101 
Contrast  in  pictures,  51 
Counterbalancing  line  effects,  99 
Criminalistic  possibilities,  59 

D. 

Daily  Mirror,  12,  18,  49,  56,  74 
Damped  oscillations,  83 
Damping  factor,  119 

of      galvanometer 

strings,  69,  85 
Direct  engraving  by  telegraphy, 

8,9 
Distortion  of  image,  95 

counteraction  of,  95 
Duddell,  82 
Duplex  working  of  telautograph, 

79 

E. 

EARTH  "  return,"  74 
Einthoverf  galvanometer,  36,  61, 
64,  82 


144 


INDEX 


Electrolytic  receiver,  91 
Elongation  of  pictures,  42 
Engraving,    direct    telegraphic, 
8,9 

F. 

FASHION  pictures,  77 

Fatigue  of  selenium,  46 

Fire  at  Paris  telephone  ex- 
change, 56 

First  photograph  wired  to  Lon- 
don, 50 

Franco-British  Exhibition,  56 

Frequency  meter,  42 

G. 

GALVANOMETER,  current,  80 

Korn's,      con- 
struction of, 

34 

wire,      lateral 
displace- 
ment, 35 
Gamble,  Mr.  Wm.,  8 

predictions,  19 
Glatzel,  Dr.,  48,  72 
Grand  National  race,  74 
Grzanna  telautograph,  n 

H. 

HARTMANN  -  KEMPF    frequency 

meter,  42 

Haselden,  Mr.  W.  K.,  12 
Heaviside,  95 

I. 

Illustration,  48,  72 
Imperial   International  Exhibi- 
tion, 97 


Inductance  of  line,  95 
Induction  effects,  54 
Installation  described,  57 
Iridium  stylus,  65,  92 

J- 

JIGGER,    in   wireless  apparatus, 
134 

K. 

KNUDSEN,    Mr.    Hans,    wireless 

apparatus.  128 
Korn,  Prof.  A.,  7,  62,  66 

photograph    of, 

46 

Korn's  compensation  method,  29 
galvanometer  ;      photo- 
graph, 38 

receiving  apparatus,  33 
selenium  transmitter,  24 
telautograph,  61 


L. 

LEAKANCE,  53,  95 
Line  balancer,  89,  92 
Line  photographs,  102 
Lined    appearance     of     photo- 
graphs, 51 
Lines,  telephone,  resistance,  etc., 

of,  108 

weight  of,  112 
Lokal  Anzeiger,  49,  72 

M. 

MAGNESIUM  shutter.  34 
Manchester  Courier,  57 
Matin,  Le.  72 


INDEX 


145 


Meyer,  n 

Microphone,  use  of,  14 
Morse  induction,  54 
Motive  power,  64 

N. 

NEGATIVE       photographs      for 

transmission,  102 
Nernst  lamp,  24,  33,  68,  120 

o. 

O'MEARA,  Major,  49 
Oscillograph,  Blondel,  119 
Oscillographic  records,  in 

P. 

PAPER,  conductive,  98 

Perry,  Prof.,  4 

Photographs,  half-tone,  99,  101 

single  line,  103 
Polarisation  receiver,  17 
Postal  strike  in  Paris.  73 
Pupin,  113 

R. 

RECEIVING  apparatus,  Korn's 
telautograph,  67 

Regulating  resistance  on  re- 
ceiver, 68 

Regulator  of  Thorne-Baker 
telectrograph,  94 

Relay,  polarised,  44 

Relief    photographs, 


transmit 
ting,  9 
used      by 
Belin,  116 


Retouching,  58 
Reversing  gear,  70 

P.T. 


Rheostat,  Belin's,  118 
Ruhmer,  Dr.,  32,  60 

s. 

SANGER-SHEPHERD,  65,  72,  89 
Scale  of  tints, 'Belin's,  120 
Selenium,  4,  22,  24 

colour    sensitiveness 

of,  32 

inertia  of,  26 
Korn's  compensation 

for  inertia,  26 
Sharman,  16 
Shunt  resistance,  36 

circuit  on  line,  93 
Siemens  and  Halske  relay,  44 
Snapshots,  telegraphy  of,  61 
Sodium  sulphate  cells,  66 
Standard  cable,  112 
Stylus,  construction  of,  65 
iridium,  65,  92 
sparking  at,  66 
Submarine  cable,  113 
Switchboard,  45 
Synchronising  of  apparatus,  36, 
39-  89,  98 

T. 

TANDY,  Mr.  F.,  49 
Telautograph,  Korn's,  61 

principles  of,  63 
receiving  on  pho- 
tographic 
paper,  78 
Telectrograph,  receiver,  93 

as  recorder,  114 
Telegraphy,  duplex  system,  use 

of,  107 
Telestereograph,  Belin's,  116 


146 


INDEX 


Telewriter,  n 

Thorne-Baker  telectrograph,  88 
Transatlantic  possibilities,  60 
Tucker,    Mr.   A.   H.,  operating 
Korn's  telautograph  ;    photo- 
graph, see  Frontispiece 
Typewriting,    transmission     of, 


w. 


WAVE-LENGTH,  effect  on  inertia 

of  selenium,  32 
Wheatstone  bridge,  30 

Belin's    use 

of.  123 

Will,  Herr,  48 
Wipe-out  current,  113 


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Del  Mar,  W.  A.     Electric  Power  Conductors 8vo,  *2  oo 

Denny,  G.  A.     Deep-Level  Mines  of  the  Rand 4to,  *io  oo 

—  Diamond  Drilling  for  Gold *5  oo 

Derr,  W.  L.     Block  Signal  Operation Oblong  i2mo,  *i  50 

Desaint,  A.     Three  Hundred  Shades  and  How  to  Mix  Them.  .8vo,  *io  oo 

Dibdin,  W.  J.     Public  Lighting  by  Gas  and  Electricity ,8vo,  *8  oo 

—  Purification  of  Sewage  and  Water 8vo,  6  50 

Dietrich,  K.     Analysis  of  Resins,  Balsams,  and  Gum  Resins  .8vo,  *3  oo 
Dinger,  Lieut.  H.  C.     Care  and  Operation  of  Naval  Machinery 

i2mo.  *2  oo 

Dixon,  D.  B.     Machinist's  and  Steam  Engineer's  Practical  Cal- 
culator   i6mo,  mor.,  i  25 

Doble,  W.  A.     Power  Plant  Construction  on  the  Pacific  Coast. 

(In  Press.) 
Dodd,  G.     Dictionary  of  Manufactures,  Mining,  Machinery,  and 

the  Industrial  Arts i2mo,  i  50 

Dorr,  B.  F.     The  Surveyor's  Guide  and  Pocket  Table-book. 

i6mo,  mor.,  2  oo 

Down,  P.  B.     Handy  Copper  Wire  Table i6mo,  *i  oo 

Draper,    C.    H.     Elementary   Text-book    of    Light,    Heat   and 

Sound -  - i2mo,  i  oo 

Heat  and  the  Principles  of  Thermo-dynamics i2mo,  i  50 

Duckwall,  E.  W.     Canning  and  Preserving  of  Food  Products 

§vo,  *$  oo 


D.  VAN  NOSTRAND  COMPANY^  SHORT-TITLE  CATALOG  9 

Dumesny,  P.,  and  Noyer,  J.  Wood  Products,  Distillates,  and 

Extracts 8vo,  *4  50 

Duncan,  W.  G.,  and  Penman,  D.  The  Electrical  Equip  nent  of 

Collieries 8vo,  *4  oo 

Duthie,  A.  L.  Decorative  Glass  Processes.  (Westminster 

Series) 8vo,  *2  oo 

Dyson,  S.  S.     Practical  Testing  of  Raw  Materials 8vo,  *5  oo 

Eccles,  R.  G.,  and  Duckwall,  E.  W.     Food  Preservatives  . . .  .8vo,  i  oo 

paper,  o  50 

Eddy,  H.  T.     Researches  in  Graphical  Statics 8vo,  i  50 

—  Maximum  Stresses  under  Concentrated  Loads 8vo,  i  50 

Edgcumbe,  K.     Industrial  Electrical  Measuring  Instruments. 

8vo,  *2  50 

Eissler,  M.     The  Metallurgy  of  Gold 8vo,  7  50 

—  The  Hydrometallurgy  of  Copper 8vo,  *4  50 

—  The  Metallurgy  of  Silver 8vo,  4  oo 

—  The  Metallurgy  of  Argentiferous  Lead ." 8vo,  5  oo 

—  Cyanide  Process  for  the  Extraction  of  Gold 8vo,  3  oo 

—  A  Handbook  of  Modern  Explosives 8vo,  5  oo 

Ekin,  T.  C.     Water  Pipe  and  Sewage  Discharge  Diagrams . .  folio,  *3  oo 
Eliot,  C.  W.,  and  Storer,  F.  H.    Compendious  Manual  of  Qualita- 
tive Chemical  Analysis i2mo,  *i  25 

Elliot,  Major  G.  H.     European  Light-house  Systems 8vo,  5  oo 

Ennis,  Wm.  D.     Linseed  Oil  and  Other  Seed  Oils   8vo,  *4  oo 

—  Applied  Thermodynamics 8vo,  *4  50 

Erfurt,  J.     Dyeing  of  Paper  Pulp.     Trans,  by  J.  Hubner.  ..8vo,  *7  50 

Erskine -Murray,  J.     A  Handbook  of  Wireless  Telegraphy ..  8vo,  *3  50 

Evans,  C.  A.     Macadamized  Roads (In  Press.) 

Ewing,  A.  J.     Magnetic  Induction  in  Iron 8vo,  *4  oo 

Fairie,  J.     Notes  on  Lead  Ores i2mo,  *i  o 

—  Notes  on  Pottery  Clays i2mo,  *i  50 

Fairweather,  W.  C.     Foreign  and  Colonial  Patent  Laws  . .  .8vo,  *3  oo 

Fanning,  T.  T.     Hydraulic  and  Water-supply  Engineering  .8vo,  *5  oo 
Fauth,  P.     The  Moon  in  Modern  Astronomy.     Trans,   by  J. 

McCabe 8vo,  *2  oo 

Fay,  I.  W.     The  Coal-tar  Colors 8vo  (In  Press.) 

Fernbach,  R.  L.    Glue  and  Gelatine 8vo,  *3  oo 


10     D.  VAN  NOSTRAND  COMPANY'S  SHORT-TITLE  CATALOG 

Fischer,  E.     The  Preparation  of  Organic  Compounds.     Trans. 

by  R.  V.  Stanford 1 2mo,  *  i  25 

Fish,  J.  C.  L.     Lettering  of  Working  Drawings Oblong  8vo,  i  oo 

Fisher,  H.  K.  C.,  and  Darby,  W.  C.     Submarine  Cable  Testing. 

8vo>  *3  50 

Fiske,  Lieut.  B.  A.     Electricity  in  Theory  and  Practice  . . .  .8vo,  2  50 
Fleischmann,  W.     The  Book  of  the  Dairy.     Trans,  by  C.  M. 

Aikman 8 vo,  4  oo 

Fleming,    J.    A.     The    Alternate-current    Transformer.     Two 

Volumes 8vo, 

Vol.    I.     The  Induction  of  Electric  Currents *5  oo 

Vol.  II.     The  Utilization  of  Induced  Currents *5  oo 

—  Centenary  of  the  Electrical  Current 8vo,  *o  50 

—  Electric  Lamps  and  Electric  Lighting .- 8vo,  *3  oo 

—  Electric  Laboratory  Notes  and  Forms 4to,  *5  oo 

—  A  Handbook  for  the  Electrical  Laboratory  and  Testing 

Room.     Two  Volumes 8vo,  each,     *5  oo 

Fluery,  H.  The  Calculus  Without  Limits  or  Infinitestimals. 

Trans,  by  C.  0.  Mailloux (In  Press) 

Foley,  N.  British  and  American  Customary  and  Metric  Meas- 
ures   folio,  *3  oo 

Foster,  H.  A.  Electrical  Engineers'  Pocket-book.  (Sixth 

Edition.) . .; i2mo,  leather,  5  oo 

Foster,  Gen.  J.  G.  Submarine  Blasting  in  Boston  (Mass.) 

Harbor 4to,  3  50 

Fowle,  F.  F.     Overhead  Transmission  Line  Crossings  ..  .  .i2mo,     *i  50 

—  The  Solution  of  Alternating  Current  Problems. 

8vo  (In  Press) 
Fox,  W.,  and  Thomas,  C.  W.  Practical  Course  in  Mechanical 

Drawing . .  1 2mo,  i  25 

Francis,  J.  B.  Lowell  Hydraulic  Experiments 4to,  15  oo 

Fuller,  G.  W.  Investigations  into  the  Purification  of  the  Ohio 

River 4to,  *io  oo 

Furnell,  J.  Paints,  Colors,  Oils,  and  Varnishes 8vo,  *i  oo 

Gant,  L.  W.     Elements  of  Electric  Traction 8vo,  *2  50 

Garcke,  E.,  and  Fells,  J.  M.     Factory  Accounts 8vo,  3  oo 

Garforth,  W.  E.  Rules  for  Recovering  Coal  Mines  after  Explo- 
sions and  Fires i2mo,  leather,  i  50 


I).  VAN  NOSTRAND  COMPANY'S  SHORT-TITLE  CATALOG     11 

Geerligs,  H.  C.  P.  Cane  Sugar  and  Its  Manufacture 8vo,  *5  oo 

Geikie,  J.  Structural  and  Field  Geology 8vo,  *4  oo 

Gerber,  N.  Analysis  of  Milk,  Condensed  Milk,  and  Infants' 

Milk-Food 8vo,  i  25 

Gerhard,  W.  P.  Sanitation,  Water-supply  and  Sewage  Disposal 

of  Country  Houses i2mo,  *2  oo 

Gerhardi,  C.  W.  H.  Electricity  Meters 8vo,  *4  oo 

Geschwind,  L.  Manufacture  of  Alum  and  Sulphates.  Trans. 

by  C.  Salter 8vo,  *5  oo 

Gibbs,  W.  E.  Lighting  by  Acetylene i2mo,  *i  50 

—  Physics  of  Solids  and  Fluids.     (Carnegie  Technical  Schools 

Text-books.) *i  50 

Gibson,  A.  H.     Hydraulics  and  Its  Application 8vo,  *5  oo 

—  Water  Hammer  in  Hydraulic  Pipe  Lines i2mo,  *2  oo 

Gillmore,  Gen.  Q.  A.  Limes,  Hydraulic  Cements  and  Mortars. 8vo,  4  oo 

—  Roads,  Streets,  and  Pavements i2mo,  2  oo 

Golding,  H.  A.     The  Theta-Phi  Diagram i2mo,  *i  25 

Goldschmidt,  R.     Alternating  Current  Commutator  Motor  .8vo,  *3  oo 

,  Goodchild,  W.     Precious  Stones.     (Westminster  Series.). .  .8vo,  *2  oo 

Goodeve,  T.  M.     Textbook  on  the  Steam-engine i2mo,  2  oo 

Gore,  G.     Electrolytic  Separation  of  Metals 8vo,  *3  50 

Gould,  E.  S.     Arithmetic  of  the  Steam-engine i2mo,  i  oo 

—  Practical  Hydrostatics  and  Hydrostatic  Formulas.     (Science 

Series.) i6mo,  o  50 

Grant,  J.  Brewing  and  Distilling.  (Westminster  Series.)  8vo  (In  Press) 

Gray,  J.  Electrical  Influence  Machines i2mo,  2  oo 

Greenwood,  E.  Classified  Guide  to  Technical  and  Commercial 

Books 8vo,  *3  oo 

Gregorius,  R.  Mineral  Waxes.  Trans,  by  C.  Salter i2mo,  *3  oo 

Griffiths,  A.  B.  A  Treatise  on  Manures i2mo,  3  oo 

—  Dental  Metallurgy 8vo,  *3  50 

Gross,  E.     Hops " 8vo,  *4  50 

Grossman,  J.     Ammonia  and  its  Compounds i2mo,  *i  25 

Groth,  L.  A.     Welding  and  Cutting  Metals  by  Gases  or  Electric- 
ity  8vo,  *3  oo 

Grover,  F.     Modern  Gas  and  Oil  Engines. . .. 8vo,  *2  oo 

Gruner,  A.     Power-loom  Weaving 8vo,  *3  oo 

Giildner,    Hugo.      Internal-Combustion    Engines.      Trans,    by 

H.  Diedrichs . . ". 4to,  *io  oo 


12     D.  VAN  NOSTRAND  COMPANY'S  SHORT-TITLE  CATALOG 

Gunther,  C.  0.     Integration i2mo,  *i  25 

Gurden,  R.  L.     Traverse  Tables folio,  half  mor.  7  50 

Guy,  A.  E.     Experiments  on  the  Flexure  of  Beams 8vo,  *i   25 

Haeder,  H.     Handbook  on  the  Steam-engine.     Trans,  by  H.  H. 

P.  Powles i2mo,  3  oo 

Hainbach,  R.     Pottery  Decoration.     Trans,  by  C.  Slater.    i2mo,  *3  oo 

Hale,  W.  J.     Calculations  of  General  Chemistry i2mo,  *i  oo 

Hall,  C.  H.     Chemistry  of  Paints  and  Paint  Vehicles i2mo,  *2  oo 

Hall,  R.  H.     Governors  and  Governing  Mechanism i2mo,  *2  oo 

Hall,  W.  S.     Elements  of  the  Differential  and  Integral  Calculus 

8vo,  *2  25 

—  Descriptive  Geometry 8vo  volume  and  4to  atlas,  *3  50 

Haller,  G.  F.,  and  Cunningham,  E.  T.    The  Tesla  Coil i2mo,  *i   25 

Halsey,  F.  A.     Slide  Valve  Gears i2mo,  i  50 

—  The  Use  of  the  Slide  Rule.     (Science  Series.) i6mo,  o  50 

—  Worm  and  Spiral  Gearing.     (Science  Series.) ...  i6mo,  o  50 

Hamilton,  W.  G.     Useful  Information  for  Railway  Men. .  i6mo,  i  oo 

Hammer, W.  J.     Radium  and  Other  Radioactive  Substances,  8 vo,  *i  oo 

Hancock,  H.     Textbook  of  Mechanics  and  Hydrostatics. ...  .8vo,  i  50 

Hardy,  E.     Elementary  Principles  of  Graphic  Statics i2mo,  *i  50 

Harper,  W.  B.     Utilization  of  Wood  Waste  by  Distillation. .  4to,  *3  oo 

Harrison,  W.  B.     The  Mechanics'  Tool-book i2mo,  i  50 

Hart,  J.  W.     External  Plumbing  Work 8vo,  *3  oo 

—  Hints  to  Plumbers  on  Joint  Wiping. 8vo,  *3  oo 

—  Principles  of  Hot  Water  Supply. 8vo,  *3  oo 

—  Sanitary  Plumbing  and  Drainage. 8vo,  *3  oo 

Haskins,  C.  H.     The  Galvanometer  and  Its  Uses i6mo,  i  50 

Hatt,  J.  A.  H.     The  Colorist square  i2mo,  *i  50 

Hausbrand,  E.     Drying  by  Means  of  Air  and  Steam.     Trans. 

by  A.  C.  Wright I2mo,  *2  oo 

—  Evaporing,   Condensing  and  Cooling   Apparatus.     Trans. 

by  A.  C.  Wright 8vo,  *5  oo 

Hausner,  A.  Manufacture  of  Preserved  Foods  and  Sweetmeats. 

Trans,  by  A.  Morris  and  H.  Robson 8vo,  *3  oo 

Hawke,  W.  H.  Premier  Cipher  Telegraphic  Code 4to,  *5  oo 

—  100,000  Words  Supplement  to  the  Prenier  Code..  .  .  .  .410,  *5  oo 

Hawkesworth,  J.     Graphical  Handbook  for  Raniforced  Concrete 

Design : 4to,  *2  50 


D.  VAN  NOSTRAND  COMPANY'S  SHORT-TITLE  CATALOG     13 

Hay,  A.  Alternating  Currents.  . 8vo,  *2  50 

—  Principles  of  Alternate-current  Working i2mo,  2  oo 

—  Electrical  Distributing  Networks  and  Distributing  Lines.Svo,  *3  50 

—  Continuous  Current  Engineering 8vo,  *2  50 

Heap,  Major  D.  P.     Electrical  Appliances ....  8vo,  2  oo 

Heaviside,    0.     Electromagnetic    Theory.     Two    volumes. 

8vo,  each,  *5  oo 

Heck,  R.  C.  H.     Stearn-Engine  and  Other  Steam  Motors.     Two 
Volumes. 

Vol.    I.     Thermodynamics  and  the  Mechanics 8vo,  *3  50 

Vol.  II.     Form,  Construction  and  Working 8vo,  *5  oo 

~  Abridged  edition  of  above  volumes  (Elementary) 

8vo  (In  Preparation) 

— •  Notes  on  Elementary  Kinematics 8vo,  boards,  *i  oo 

—  Graphics  of  Machine  Forces 8vo,  boards,  *i  oo 

Hedges,  K.     Modern  Lightning  Conductors 8vo,  3  oo 

Heermann,  P.     Dyers*  Materials.     Trnas.  by  A.  C.  Wright.  i2mo,  *2  50 
Hellot,  Macquer  and  D'Apligny.     Art  of  Dyeing  Wool,  Silk  and 

Cotton 8vo,  *2  oo 

Henrici,  O.  Skeleton  Structures 8vo,  i  50 

Hermann,  F.  Painting  on  Glass  and  Porcelain 8vo,  *3  50 

Hermann,  G.  The  Graphical  Statics  of  Mechanism.  Trans. 

by  A.  P.  Smith i2mo,  2  oo 

Herzfeld,  J.  Testing  of  Yarns  and  Textile  Fabrics ,  .8vo,  *3  50 

Hildebrandt,  A.  Airships,  Past  and  Present 8vo,  *3  50 

Hill,  J.  W.  The  Purification  of  Public  Water  Supplies.  New 

Edition (In  Press.) 

—  Interpretation  of  Water  Analysis (In  Press.) 

Hiroi,  I.     Statically-Indeterminate  Stresses. i2mo,  *2  oo 

Hirshfeld,    C.    F.      Engineering     Thermodynamics.     (Science 

Series.) i6mo,  o  50 

Hobart,  H.  M.     Heavy  Electrical  Engineering.. 8vo,  *4  50 

—  Electricity 8vo,  *2  oo 

—  Electric  Trains 8vo,  *2  50 

Hobbs,  W.  R.  P.     The  Arithmetic  of  Electrical  Measurements 

i2mo,  o  50 

Hoff,  J.  N.     Paint  and  Varnish  Facts  and  Formulas.  ....  i2mo,  *3  oo 
Hoff,  Com.W.  B.  The  Avoidance  of  Collisions  at  Sea.  i6mo,  mor.,     o  75 

Hole,  W.     The  Distribution  of  Gas 8vo,  *7  50 


14     D.  VAN  NOSTRAND  COMPANY'S  SHORT-TITLE  CATALOG 

Holley,  A.  L.     Railway  Practice folio,  12  oo 

Holmes,  A.  B.     The  Electric  Light  Popularly  Explained. 

i2mo,  paper,  o  50 

Hopkins,  N.  M.     Experimental  Electrochemistry 8vo,  *3  oo 

—  Model  Engines  and  Small  Boats I2mo,  i  25 

Homer,  J.     Engineers'  Turning 8vo,  *3  50 

—  Metal  Turning. i2mo,  i  50 

—  Toothed  Gearing r i2mo,  2  25 

Houghton,  C.  E.     The  Elements  of  Mechanics  of  Materials.  i2mo,  *2  oo 

Houllevique,  L.     The  Evolution  of  the  Sciences 8vo,  *2  oo 

Howe,  G.     Mathematics  for  the  Practical  Man i2mo  (In  Press.) 

Howorth,  J.     Repairing  and  Riveting  Glass,  China  and  Earthen- 
ware  8vo,  paper,  *o  50 

Hubbard,  E.     The  Utilization  of  Wood-waste 8vo,  *2  50 

Humber,  W.     Calculation  of  Strains  in  Girders i2mo,  2  50 

Humphreys,    A.    C.     The    Business    Features    of    Engineering 

Practice..... 8vo,  *i  25 

Hurst,  G.  H.     Handbook  of  the  Theory  of  Color 8vo,  *2  50 

—  Dictionary  of  Chemicals  and  Raw  Products 8vo,  *3  oo 

—  Lubricating  Oils,  Fats  and  Greases 8vo,  *3  oo 

—  Soaps 8vo,  *5  oo 

—  Textile  Soaps  and  Oils 8vo,  *2  50 

Hutchinson,  R.  W.,  Jr.     Long  Distance  Electric  Power  Trans- 
mission  i2mo,  *3  oo 

Hutchinson,  R.  W.,  Jr.,  and  Ihlseng,  M.  C.  Electricity  in 

Mining i2mo  (In  Press.) 

Hutchinson,  W.  B.  Patents  and  How  to  Make  Money  Out  of 

Them. i2mo,  i  25 

Button,  W.  S.     Steam-boiler  Construction 8vo,  6  oo 

—  Practical  Engineer's  Handbook 8vo,  7  oo 

—  The  Works'  Manager's  Handbook 8vo,  6  oo 

Ingle,  H.     Manual  of  Agricultural  Chemistry 8vo,  *3  oo 

Innes,  C.  H.     Problems  in  Machine  Design i2mo,  *2  oo 

Air  Compressors  and  Blowing  Engines.. ...... i2mo,  *2  oo 

—  Centrifugal  Pumps i2mo,  *2  oo 

—  The  Fan i2mo,  *2  oo 

Isherwood,  B.  F.     Engineering  Precedents  for  Steam  Machinery 

8vo,     2  50 


D.  VAN  NOSTKAND  COMPANY'S  SHORT-TITLE  CATALOG     15 

Jamieson,  A.     Text  Book  on  Steam  and  Steam  Engines. .  .  .  8vo,  3  oo 

—  Elementary  Manual  on  Steam  and  the  Steam  Engine  .  12  mo,  i  50 
Jannettaz,  E.     Guide  to  the  Determination  of  Rocks.     Trans. 

by  G.  W.  Plympton izmo,  i  50 

Jehl,  F.     Manufacture  of  Carbons 8vo,  *4  oo 

Jennings,    A.    S.     Commercial   Paints   and   Painting.     (West- 
minster Series.) 8vo  (In  Press.) 

Jennison,  F.  H.     The  Manufacture  of  Lake  Pigments 8vo,  *3  oo 

Jepson,  G.     Cams  and  the  Principles  of  their  Construction. . .  8vo,  *i  50 

-  Mechanical  Drawing .8vo  (In  Preparation.) 

Jockin,  W.     Arithmetic  of  the  Gold  and  Silversmith i2mo,  *i  oo 

Johnson,  G.  L.     Photographic  Optics  and  Color  Photography 

8vo,  *3  oo 
Johnson,    W.    H.     The  Cultivation  and   Preparation    of    Para 

Rubber 8vo,  *3  oo 

Johnson,  W.  McA.     The  Metallurgy  of  Nickel (In  Preparation.) 

Johnston,  J.  F.  W.,  and  Cameron,  C.     Elements  of  Agricultural 

Chemistry  and  Geology i2mo,  2  60 

Joly,  J.     Radioactivity  and  Geology i2mo,  *3  oo 

Jones,  H.  C.     Electrical  Nature  of  Matter  and  Radioactivity 

i2mo,  2  oo 

Jones,  M.  W.     Testing  Raw  Materials  Used  in  Paint i2mo,  *2  oo 

Jones,  L.,  and  Scard,  F.  I.     Manufacture  of  Cane  Sugar 8vo,  *5  oo 

Joynson,  F.  H.     Designing  and  Construction  of  Machine  Gear- 
ing  8vo,  2  oo 

Juptner,  H.  F.  V.     Siderology :  The  Science  of  Iron 8vo,  *5  oo 

Kansas  City  Bridge 4to,  6  oo 

Kapp,  G.     Electric  Transmission  of  Energy i2mo,  3  50 

—  Dynamos,    Motors,    Alternators   and   Rotary    Converters. 

Trans,  by  H.  H.  Simmons 8vo,  4  oo 

Keim,  A.  W.     Prevention  of  Dampness  in  Buildings 8vo,  *2  oo 

Keller,  S.  S.     Mathematics  for  Engineering  Students. 

i2mo,  half  leather, 

—  Algebra  and  Trigonometry,  with  a  Chapter  on  Vectors. ...  *i  75 

—  Special  Algebra  Edition *i  oo 

Plane  and  Solid  Geometry , *i  25 

Analytical  Geometry  and  Calculus *2  oo 

Kelsey,  W.  R.     Continuous-current  Dynamos  and  Motors..  .8  vo,  *2  50 


16     D.  VAN  NOSTRAND  COMPANY'S  SHORT-TITLE  CATALOG 

Kemble,  W.  T.,  and  Underbill,  C.  R.     The  Periodic  Law  and  the 

Hydrogen   Spectrum 8vo,  paper,  *o  50 

Kemp,  J.  F.     Handbook  of  Rocks 8vo,  *i  50 

Kendall,  E.     Twelve  Figure  Cipher  Code 4to,  *i5  oo 

Kennedy,    R.     Modern   Engines   and   Power   Generators.     Six 

Volumes , 4to,  15  oo 

Single  Volumes each,  3  oo 

—  Electrical  Installations.     Five  Volumes 4to,  15  oo 

Single  Votumes each,  3  50 

—  Flying  Machines;  Practice  and  Design i2mo,  *2  oo 

Kennelly,  A.  E.     Electro-dynamic  Machinery 8vo,  i  50 

Kershaw,  J.  B.  C.     Fuel,  Water  and  Gas  Analysis 8vo,  *2  50 

Electrometallurgy.     (Westminster  Series.) 8vo,  *a  oo 

—  The  Electric  Furnace  in  Iron  and  Steel  Pr eduction.. i2mo,  *i  50 

Kingdon,  J.  A.     Applied  Magnetism 8vo,  *3  oo 

Kinzbrunner,  C.     Alternate  Current  Windings 8vo,  *i  50 

—  Continuous  Current  Armatures -. 8vo,  *i  50 

Testing  of  Alternating  Current  Machines 8vo,  *2  oo 

Kirkaldy,    W.    G.     David    Kirkaldy's    System    of    Mechanical 

Testing 4to,  10  oo 

Kirkbride,  J.     Engraving  for  Illustration 8vo,  *i  50 

Kirkwood,  J.  P.     Filtration  of  River  Waters 4to,  7  50 

Klein,  J.  F.     Design  of  a  High  speed  Steam-engine 8vo,  *5  oo 

Kleinhans,  F.  B.     Boiler  Construction 8vo,  3  oo 

Knight,  Capt.  A.  M.     Modern  Steamship 8vo,  *7  50 

Half  Mor.  *g  oo 

Knox,  W.  F.     Logarithm  Tables (In  Preparation.) 

Knott,  C.  G.,  and  Mackay,  J.  S.     Practical  Mathematics.  .  .8vo,  2  oo 

Koester,  F.     Steam-Electric  Power  Plants 4to,  *5  oo 

—  Hydroelectric  Developments  and  Engineering -4to,  *5  oo 

Koller,  T.     The  Utilization  of  Waste  Products 8vo,  *3  50 

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Krauch,  C.     Testing  of  Chemical  Reagents.     Trans,  by  J.  A. 

Williamson  and  L.  W.  Dupre 8vo,  *3  oo 

Lambert,  T.     Lead  and  its  Compounds 8vo,  *3  50 

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Lamborn,  L.  L.     Cottonseed  Products 8vo,  *3  oo 

Modern  Soaps,  Candles,  and  Glycerin 8vo,  *7  50 


D.  VAN  NOSTRAND  COMPANY'S  SHORT-TITLE  CATALOG     17 

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Lamer,  E.  T.     Principles  of  Alternating  Currents i2mo,  *i  25 

Larrabee,   C.   S.     Cipher   and   Secret   Letter   and   Telegraphic 

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Lassar-Cohn,  Dr.     Modern  Scientific  Chemistry.     Trans;  by  M. 

M.  Pattison  Muir izmo,  *2  oo 

Latta,  M.  N.     Handbook  of  American  Gas-Engineering  Practice. 

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Leask,  A.  R.     Breakdowns  at  Sea i2mo,  2  oo 

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Lecky,  S.  T.  S.     "  Wrinkles  "  in  Practical  Navigation 8vo,  *8  oo 

Leeds,  C.  C.    Mechanical  Drawing  for  Trade  Schools .  oblong,  4to, 

High  School  Edition *i  25 

Machinery  Trades  Edition *2  oo 

Lefe"vre,  L.     Architectural  Pottery.     Trans,  by  H.  K.  Bird  and 

W.  M.  Binns 410,  *7  50 

Lehner,  S.     Ink  Manufacture.     Trans,  by  A.  Morris  and  H. 

Robson 8vo,  *2  50 

Lemstrom,  S.     Electricity  in  Agriculture  and  Horticulture. 

8vo,  *i  50 
Lewes,  V.  B.     Liquid  and  Gaseous  Fuels.     (Westminster  Series.) 

8vo,  *2  oo 

Lieber,  B.  F.     Lieber's  Standard  Telegraphic  Code 8vo,  *io  oo 

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18     D.  VAN  NOSTRAND  COMPANY'S  SHORT-TITLE  CATALOG 

Livermore,  V.  P.,  and  Williams,  J.     How  to  Become  a  Com- 
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Livingstone,  R.     Design  and  Construction  of  Commutators.  8vo,  *2  25 

Lobben,  P.     Machinists'  and  Draftsmen's  Handbook  ......  8vo,  2  50 

Locke,  A.  G.  and  C.  G.     Manufacture  of  Sulphuric  Acid  .....  8vo,  10  oo 

Lockwood,  T.  D.     Electricity,  Magnetism,  and  Electro-teleg- 

graphy 8vo,  2  50 

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Lodge,  O.  J.     Elementary  Mechanics i2mo,  i  50 

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Lord,  R.  T.     Decorative  and  Fancy  Fabrics 8vo,  *3  50 

Loriag,  A.  E.     A  Handbook  of  the  Electromagnetic  Telegraph. 

i6mo,       o  50 

Lowenstein,  L.  C.,  and  Crissey,  C.  P.     Centrifugal  Pumps.     (In  Press.) 
Lucke,  C.  E.     Gas  Engine  Design 8vo,     *3  oo 

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2  vols (In  Preparation.) 

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paper,     *i  50 

Lunge,  G.     Coal-tar  Ammonia.     Two  Volumes... 8vo,  *i5  oo 

Manufacture  of  Sulphuric  Acid  and  Alkali.     Three  Volumes 

8vo, 

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Vol.  II.     Salt  Cake,  Hydrochloric  Acid  and  Leblanc  Soda. 

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Vol.  III.     Ammonia  Soda *I5  oo 

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Technical  Methods  of  Chemical  Analysis.     Trans,  by  C.  A. 

Keane.     In  collaboration  with  the  corps  of  spscialists. 

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Lupton,  A.,  Parr,  G.  D.  A.,  and  Perkin,  H.     Electricity  as  Applied 

to  Mining 8vo,     *4  50 

Luquer,  L.  M.     Minerals  in  Rock  Sections 8vo,     *i  50 

Macewen,  H.  A.     Food  Inspection 8vo,  *2  50 

Mackie,  J.     How  to  Make  a  Woolen  Mill  Pay 8vo,  *2  oo 

Mackrow,    C.     Naval    Architect's    and    Shipbuilder's    Pocket- 
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D.  VAN  NOSTIIAND  COMPANY'S  SHORT-TITLE  CATALOG     19 

Maguire,  Capt.  E. ,   The  Attack  and  Defense  of  Coast  Fortifica- 
tions  8vo,  2  50 

Maguire,  Wm.  R.     Domestic  Sanitary  Drainage  and  Plumbing 

8vo,  4  oo 
Marks,  E.  C.  R.     Construction  of  Cranes  and  Lifting  Machinery 

i2mo,  *i  50 

—  Construction  and  Working  of  Pumps i2mo,  *i  50 

—  Manufacture  of  Iron  and  Steel  Tubes i2mo,  *2  oo 

—  Mechanical  Engineering  Materials I2mo,  *i  oo 

Marks,  G.  C.     Hydraulic  Power  Engineering .8vo,  3  50 

—  Inventions,  Patents  and  Designs. i2mo,  *i  oo 

Markham,  E.  R.     The  American  Steel  Worker i2mo,  2  50 

Marlow,  T.  G.     Drying  Machinery  and  Practice 8vo, 

Marsh,  C.  F.     Concise  Treatise  on  Reinforced  Concrete.. .  .8vo,  *2  50 

Marsh,  C.  F.,  and  Dunn,  W.     Reinforced  Concrete 4to,  *5  oo 

—  Manual  of  Reinforced  Concrete  and  Concrete  Block  Con- 

struction  i6mo,  mor.,  *2  50 

Massie,  W.  W.,  and  Underbill,  C.  R.     Wireless  Telegraphy  and 

Telephony I2mo,  *i  oo 

Matheson,  D.     Australian  Saw-Miller's  Log  and  Timber  Ready 

Reckoner. i2mo,  leather,  i  50 

Mathot,  R.  E.     Internal  Combustion  Engines 8vo, 

Maurice,  W.     Electric  Blasting  Apparatus  and  Explosives  ..8vo,  *3  50 

—  Shot  Firer's  Guide 8vo,  *i  50 

Maxwell,  W.  H.,  and  Brown,  J.  T.     Encyclopedia  of  Municipal 

and  Sanitary  Engineering 4to,  *io  oo 

Mayer,  A.  M.     Lecture  Notes  on  Physics. 8vo,  2  oo 

McCullough,  R.  S.     Mechanical  Theory  of  Heat 8vo,  3  50 

Mclntosh,  J.  G.     Technology  of  Sugar '.  .  .  8vo,  *4  50 

—  Industrial  Alcohol 8vo,  *3  oo 

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Volumes.     8vo. 

Vol.     I.     Oil  Crushing,  Refining  and  Boiling *3  50 

Vol.  II.     Varnish  Materials  and  Oil  Varnish  Making *4  oo 

Vol.  Ill (In  Preparation.) 

McMechen,  F.  L.     Tests  for  Ores,  Minerals  and  Metals.. .  i2mo,  *i  oo 

McNeill,  B.     McNeill's  Code :* 8vo,  *6  oo 

McPherson,  J.  A.     Water-works  Distribution 8vo,  2  50 

Melick,  C.  W.     Dairy  Laboratory  Guide I2mo,  *i  25 


20  D.  VAN  NOSTRAND  COMPANY'S  SHORT-TITLE  CATALOG 

Merck,  E.     Chemical  Reagents;  Their  Purity  and  Tests.  ..  .8vo,  *i  50 

Merritt,  Wm.  H.  Field  Testing  for  Gold  and  Silver .  i6mo,  leather,  i  50 
Meyer,  J.  G.  A.,  and  Pecker,  C.  G.     Mechanical  Drawing  and 

Machine  Design 4to,  5  oo 

Michell,  S.     Mine  Drainage 8vo,  10  oo 

Mierzinski,  S.     Waterproofing  of  Fabrics.     Trans,  by  A.  Morris 

and  H.  Robson 8vo,  *2  50 

Miller,  E.  H.     Quantitative  Analysis  for  Mining  Engineers ..  8vo,  *i  50 

Milroy,  M.  E.  W.     Home  Lace -making i2mo,  *i  oo 

Minifie,  W.     Mechanical  Drawing 8vo,  *4  oo 

Modern  Meteorology i2mo,  i  50 

Monckton,  C.  C.  F.     Radiotelegraphy.     (Westminster  Series.) 

8vo,  *2  oo 
Monteverde,  R.  D.     Vest  Pocket  Glossary  of  English-Spanish, 

Spanish-English  Technical  Terms 641110,  leather,  *i  oo 

Moore,  E.  C.  S.     New  Tables  for  the  Complete  Solution  of 

Ganguillet  and  Kutter's  Formula 8vo,  *5  oo 

Moreing,  C.  A.,  and  Neal,  T.     New  General  and  Mining  Tele- 
graph Code 8vo,  *5  oo 

Morgan,  A.  P.     Wireless  Telegraph  Construction  for  Amateurs. 

i2mo,  *i  50 

Moses,  A.  J.     The  Characters  of  Crystals 8vo,  *2  oo 

Moses,  A.  J.,  and  Parsons,  C.  I.     Elements  of  Mineralogy.  .8vo,  *2  50 
Moss,    S.    A.     Elements    of    Gas    Engine    Design.     (Science 

Series.) i6mo,  o  50 

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Mullin,  J.  P.     Modern  Moulding  and  Pattern- making   .    .  i2mo,  2  50 
Munby,  A.  E.     Chemistry  and  Physics  of  Building  Materials. 

(Westminster  Series.). 8vo,  *2  oo 

Murphy,  J.  G.     Practical  Mining i6mo,  i  oo 

Murray,  J.  A.     Soils  and  Manures.     (Westminster  Series.)  .8vo,  *2  oo 

Naquet,  A.     Legal  Chemistry i2mo,  2  oo 

Nasmith,  J.     The  Student's  Cotton  Spinning 8vo,  3  oo 

Nerz,  F.     Searchlights.     Trans,  by  C.  Rodger s 8vo,  *3  oo 

Neuberger,   H.,   and  Noalhat,   H.     Technology   of  Petroleum. 

Trans,  by  J.  G.  Mclntosh 8vo,  *io  oo 

Newall.  J.  W,      Drawing,  Sizing  and  Cutting  Bevel-gears. 

8vo,  i  50 


D.  VAN  NOSTRAND  COMPANY'S  SHORT-TITLE  CATALOG    21 

Newlands,  J.     Carpenters  and  Joiners*  Assistant 

folio,  half  mor.,  15  oo 

Nicol,  G.     Ship  Construction  and  Calculations 8vo,  *4  50 

Nipher,  F.  E.     Theory  of  Magnetic  Measurements i2mo,  i  oo 

Nisbet,  H.     Grammar  of  Textile  Design 8vo,  *3  oo 

Noll,  A.     How  to  Wire  Buildings i2mo,  i  50 

Nugent,  E.     Treatise  on  Optics i2mo,  i  50 

O'Connor,  H.     The  Gas  Engineer's  Pocketbook. .  .  i2mo,  leather,  3  50 

—  Petrol  Air  Gas i2mo,  *o  75 

Olsen,  J.  C.     Text  book  of  Quantitative  Chemical  Analysis  ..8vo,  *4  oo 
Olsson,  A.     Motor  Control,  in  Turret  Turning  and  Gun  Elevating. 

(U.  S.  Navy 'Electrical  Series,  No.  i.)  .  ...i2mo,  paper,  *o  50 

Oudin,  M.  A.     Standard  Polyphase  Apparatus  and  Systems  . .  8vo,  *3  'Do 

Palaz,  A.     Industrial  "Photometry.     Trans,  by  G.  W.  Patterson, 

Jr 8vo,  *4  oo 

Pamely,  C.     Colliery  Manager's  Handbook 8vo,  *io  oo 

Parr,  G.  D.  A.     Electrical  Engineering  Measuring  Instruments. 

8vo,  *3  50 

Parry,  E.  J.     Chemistry  of  Essential  Oils  and  Artificial  Per- 
fumes  8vo,  *5  oo 

Parry,  E.  J.,  and  Coste,  J.  H.     Chemistry  of  Pigments 8vo,  *4  50 

Parry,  L.  A.     Risk  and  Dangers  of  Various  Occupations 8vo,  *3  oo 

Parshall,  H.  F.,  and  Hobart,  H.  M.     Armature  Windings  ....  4to,  *7  50 

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Parshall,  H.  F.,  and  Parry,  E.     Electrical  Equipment  of  Tram- 
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Parsons,  S.  J.     Malleable  Cast  Iron 8vo,  *2  50 

Passmore,  A.  C.     Technical  Terms  Used  in  Architecture  ...8vo,  *3  50 

Patterson,  D.     The  Color  Printing  of  Carpet  Yarns 8vo,  *3  50 

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Patton,  H.  B.     Lecture  Notes  on  Crystallography 8vo,  *i  25 

Paulding,  C.  P.     Condensation  of  Steam  in  Covered  and  Bare 

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Peirce,  B.     System  of  Analytic  Mechanics 4to,  10  oo 


22    D.  VAN  NOSTRAND  COMPANY'S  SHORT-TITLE  CATALOG 

Pendred,  V.     The  Railway  Locomotive.     (Westminster  Series.) 

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Perkin,  F.  M.  Practical  Methods  of  Inorganic  Chemistry.  i2mo,  *i  oo 

Perrigo,  0.  E.     Change  Gear  Devices 8vo,  i  oo 

Perrine,  F.  A.  C.     Conductors  for  Electrical  Distribution  .  .  .  8vo,  *3  50 

Perry,  J.     Applied  Mechanics 8vo,  *2  50 

Petit,  G.     White  Lead  and  Zinc  White  Paints 8vo,  *i  50 

Petit,  R.     How  to  Build  an  Aeroplane.     Trans,   by  T.   O'B. 

Hubbard,  and  J.  H.  Ledeboer 8vo,  *i  50 

Phillips,  J.     Engineering  Chemistry 8vo,  *4  50 

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Phin,  J.     Seven  Follies  of  Science i2mo,  *i  25 

Household  Pests,  and  How  to  Get  Rid  of  Them 

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Plane  Table,  The 8vo,  2  oo 

Plattner's  Manual  of    Blowpipe  Analysis.     Eighth  Edition,  re- 
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Plympton,  G.  W.     The  Aneroid  Barometer.     (Science  Series.) 

i6mo,  o  50 

Pocket  Logarithms  to  Four  Places.     (Science  Series.) i6mo,  o  50 

leather,  i  oo 

Pope,  F.  L.     Modern  Practice  of  the  Electric  Telegraph. ..   8vo,  150 
Popplewell,  W.   C.     Elementary  Treatise   on  Heat  and  Heat 

Engines I2mo,  *3  oo 

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Potter,  T.     Concrete 8vo,  *3  oo 

Practical  Compounding  of  Oils,  Tallow  and  Grease 8vo,  *3  50 

Practical  Iron  Founding .' i2mo,  i  50 

Pray,  T.,  Jr.     Twenty  Years  with  the  Indicator. 8vo,  2  50 

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D.  VAN  NOSTRAND  COMPANY'S  SHORT  TITLE  CATALOG     23 

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Prescott,    A.    B.,   and   Johnson,    0.    C.     Qualitative   Chemical 

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Prescott,  A.  B.,  and  Sullivan,  E.  C.     First  Book  in  Qualitative 

Chemistry i2mo,  *i  50 

Pritchard,  0.  G.     The  Manufacture  of  Electric-light  Carbons. 

8vo,  paper,  *o  60 
Prost,  E.     Chemical  Analysis  of  Fuels,  Ores,  Metals.     Trans. 

by  J.  C.  Smith : 8vo,  *4  50 

Pullen,  W.  W.  F.     Application  of  Graphic  Methods  to  the  Design 

of  Structures i2mo,  *2  50 

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Pulsifer,  W.  H.     Notes  for  a  History  of  Lead. 8vo,  4  oo 

Putsch,  A.     Gas  and  Coal-dust  Firing 8vo,  *3  oo 

Pynchon,  T.  R.     Introduction  to  Chemical  Physics 8vo,  3  oo 

Rafter,  G.  W.     Treatment  of  Septic  Sewage.     (Science  Series.) 

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Raikes,  H.  P.     Sewage  Disposal  Works 8vo,  *4  oo 

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Ramp,  H.  M.     Foundry  Practice (In  Press.) 

Randall,  P.  M.     Quartz  Operator's  Handbook i2mo,  2  oo 

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Rankine,  W.  J.  M.     Applied  Mechanics 8vo,  5  oo 

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Rankine,  W.  J.  M.,  and.  Bamber,  E.  F.     A  Mechanical  Text- 
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Raphael,  F.  C.     Localization  of    Faults  in  Electric  Light  and 

Power  Mains t 8vo,  *3  oo 

Rathbone,  R.  L.  B.     Simple  Jewellery 8vo,  *2  oo 

Rateau,   A.     Flow  of  Steam  through  Nozzles    and    Orifices. 

Trans,  by  H.  B.  Brydon 8vo,  *i  50 


24     D.  VAN  NOSTRAND  COMPANY'S  SHORT-TITLE  CATALOG 

Rausenberger,  F.     The  Theory  of  the  Recoil  of  Guns. .....  8vo,  *4  50 

Rautenstrauch,  W.     Notes  on  the  Elements  of  Machine  Design, 

8vo,  boards,  *i  50 

Rautenstrauch,  W.,  and  Williams,  J.  T.     Machine  Drafting  and 
Empirical  Design. 

Part   I.  Machine  Drafting 8vo,  *i  25 

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Raymond,  E.  B.     Alternating  Current  Engineering i2mo,  *2  50 

Rayner,  H.     Silk  Throwing  and  Waste  Silk  Spinning 8vo,  *2  50 

Recipes  for  the  Color,  Paint,  Varnish,  Oil,  Soap  and  Drysaltery 

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Recipes  for  Flint  Glass  Making i2mo,  *4  50 

Reed's  Engineers'  Handbook 8vo,  *5  oo 

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book  8vo,  *3  oo 

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Reinhardt,   C.   W.     Lettering  for   Draftsmen,   Engineers,   and 

Students oblong  4to,  boards,  i  oo 

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Reiser,  F.     Hardening  and  Tempering  of  Steel.     Trans,  by  A. 

Morris  and  H.  Robson i2mo,  *2  50 

Reiser,  N.     Faults  in  the  Manufacture  of  Woolen  Goods.     Trans. 

by  A.  Morris  and  H.  Robson 8vo,  *2  50 

Spinning  and  Weaving  Calculations. 8vo,  *5  oo 

Renwick,  W.  G.     Marble  and  Marble  Working 8vo,  5  oo 

Rhead,  G.  F.     Simple  Structural  Woodwork i2mo,  *i  oo 

Rhead,  G.  W.     British  Pottery  Marks 8vo,  *3  oo 

Rice,  J.  M.,  and  Johnson,  W.  W.     A  New  Method  of  Obtaining 

the  Differential  of  Functions i2mo,  o  50 

Richardson,  J.     The  Modern  Steam  Engine 8vo,  *3  50 

Richardson,  S.  S.     Magnetism  and  Electricity. . i2mo,  *2  oo 

Rideal,  S.     Glue  and  Glue  Testing 8vo,  *4  oo 

Rings,  F.     Concrete  in  Theory  and  Practice i2mo,  *2  50 

Ripper,  W.     Course  of  Instruction  in  Machine  Drawing. . .  folio,  *6  oo 
Roberts,  J.,  Jr.      Laboratory  Work  in  Electrical  Engineering. 

8vo,  *2  oo 

Robertson,  L.  S.     Water-tube  Boilers 8vo,  3  oo 

Robinson,  J.  B.     Architectural  Composition 8vo,  *2  50 


D.  VAN  NOSTRAND  COMPANY'S  SHORT-TITLE  CATALOG     25 

Robinson,  S.  W.     Practical  Treatise  on  the  Teeth  of  Wheels. 

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Roebling,  J.  A.     Long  and  Short  Span  Railway  Bridges .  .    folio,  25  oo 

Rogers,  A.     A  Laboratory  Guide  of  Industrial  Chemistry.  .  i2mo,  *i  50 

Rogers,  A.,  and  Aubert,  A.  B.     Industrial  Chemistry .  (In  Press.) 

Rollins,  W.     Notes  on  X-Light 8vo,  *7  50 

Rose,  J.     The  Pattern-makers^  Assistant 8vo,  2  50 

—  Key  to  Engines  and  Engine-running i2mo,  2  50 

Rose,  T.  K.      The  Precious  Metals.      (Westminster  Series.). 

8vo,  *2  oo 

Rosenhain,  W.  Glass  Manufacture.  (Westminster  Series.) .  .8vo,  *2  oo 
Rossiter,  J.  T.     Steam  Engines.     (Westminster  Series.) 

8vo  (In  Press.) 

Pumps  and  Pumping  Machinery.     (Westminster  Series.) 

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Roth.     Physical  Chemistry 8vo,  *2  oo 

Rouillion,  L.     The  Economics  of  Manual  Training 8vo,  2  oo 

Rowan,  F.  J.     Practical  Physics  of  the  Modern  Steam-boiler 

8vo,  7  50 

Roxburgh,  W.     General  Foundry  Practice 8vo,  *3  50 

Ruhmer,    E.     Wireless    Telephony.     Trans,    by    J.    Erskine- 

Murray 8vo,  *3  50 

Russell,  A.     Theory  of  Electric  Cables  and  Networks 8vo,  *3  oo 

Sabine,  R.  History  and  Progress  of  the  Electric  Telegraph.  i2mo,  i  25 

Saeltzer,  A.     Treatise  on  Acoustics i2mo,  i  oo 

Salomons,  D.     Electric  Light  Installations.     i2mo. 

Vol.     I.     The  Management  of  Accumulators 2  50 

Vol.    II.     Apparatus 2  25 

Vol.  III.     Applications i  50 

Sanford,  P.  G.     Nitro-explosives 8vo,  *4  oo 

Saunders,  C.  H.     Handbook  of  Practical  Mechanics i6mo,  i  oo 

leather,  i  25 

Saunnier,  C.     Watchmaker's  Handbook i2mo,  3  oo 

Sayers,  H.  M.     Brakes  for  Tram  Cars 8vo,  *i  25 

Scheele,  C.  W.     Chemical  Essays .  ^ 8vo,  *2  oo 

Schellen,  H.     Magneto-electric  and  Dynamo -electric  Machines 

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Schmall,  C.  N.     First  Course  in  Analytic  Geometry,  Plane  and 

Solid. i2mo,  half  leather,  *i  75 

Schmall,  C.  N.,  and  Schack,  S.  M.     Elements  of  Plane  Geometry 

izmo,  *i  25 

Schmeer,  L.     Flow  of  Water 8vo,  *3  oo 

Schumann,  F.     A  Manual  of  Heating  and  Ventilation. 

i2mo,  leather,  i  50 

Schwartz,  E.  H.  L.     Causal  Geology 8vo,  *2  50 

Schweizer,  V.,  Distillation  of  Resins 8vo,  *3  50 

Scott,  W.  W.     Qualitative  Chemical  Analysis.     A  Laboratory 

Manual 8vo  (In  Press.} 

Scribner,  J.  M.     Engineers'  and  Mechanics'  Companion. 

7                                                            i6mo,  leather,  i  50 
Searle,  G.  M.     "  Sumners'  Method."     Condensed  and  Improved. 

(Science  Series.) i6mo,  o  50 

Seaton,  A.  E.     Manual  of  Marine  Engineering 8vo,  6  oo 

Seaton,  A.  E.,  and  Rounthwaite,  H.  M.     Pocket-book  of  Marine 

Engineering i6mo,  leather,  3  oo 

Seeligmann,  T.,   Torrilhon,   G.   L.,  and  Falconnet,   H.     India 
Rubber  and  Gutta  Percha.     Trans,  by  J.  G.  Mclntosh 

8vo,  *5  oo 
Seidell,  A.     Solubilities  of  Inorganic  and  Organic  Substances 

8vo,  New  Edition  (In  Preparation.} 

Sellew,  W.  H.     Steel  Rails 4:0  (In  Press.} 

Senter,  G.     Outlines  of  Physical  Chemistry. i2mo,  *i  50 

Sever,  G.  F.     Electric  Engineering  Experiments  ....  8vo,  boards,  *i  oo 
Sever,  G.  F.,  and  Townsend,  F.     Laboratory  and  Factory  Tests 

in  Electrical  Engineering. 8vo,  *2  50 

Sewall,  C.  H.     Wireless  Telegraphy .   8vo,  *2  oo 

—  Lessons  in  Telegraphy i2mo,  *i  oo 

Sewell,  T.     Elements  of  Electrical  Engineering 8vo,  *3  oo 

—  The  Construction  of  Dynamos : 8vo,  *3  oo 

Sexton,  A.  H.     Fuel  and  Refractory  Materials i2mo,  *2  50 

—  Chemistry  of  the  Materials  of  Engineering i2mo,  *2  50 

—  Alloys  (Non-Ferrous) 8vo,  *3  oo 

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Seymour,  A.     Practical  Lithography 8vo,  *2  50 

—  Modern  Printing  Inks 8vo,  *2  oo 

Shaw,  P.  E.     Course  of  Practical  Magnetism  and  Electricity.  8vo,  *i  oo 


D.  VAN  NOSTRAND  COMPANY'S  SHORT-TITLE  CATALOG     27 

Shaw,  S.     History  of  the  Staffordshire  Potteries 8vo,  *3  oo 

—  Chemistry  of  Compounds  Used  in  Porcelain  Manufacture 

8vo,  *5  oo 
Sheldon,  S.,  and  Hausmann,  E.      Direct   Current   Machines. 

8vo,  *2  50 
Sheldon,  S.,  Mason,  H.,  and  Hausmann,  E.     Alternating-current 

Machines 8vo,  *2  50 

Sherer,  R.     Casein.     Trans,  by  C.  Salter 8vo,  *3  oo 

Sherriff,  F.  F.     Oil  Merchants'  Manual izmo,  *3  50 

Shields,  J.  E.     Notes  on  Engineering  Construction i2mo,  i  50 

Shock,  W.  H.     Steam  Boilers 4to,  half  mor.,  15  oo 

Shreve,  S.  H.     Strength  of  Bridges  and  Roofs 8vo,  3  50 

Shunk,  W.  F.     The  Field  Engineer i2mo,  mor.,  2  50 

Simmons,  W.   H.,  and  Appleton,   H.   A.     Handbook  of  Soap 

Manufacture. 8vo,  *3  oo 

Simms,  F.  W.     The  Principles  and  Practice  of  Leveling 8vo,  2  50 

—  Practical  Tunneling.  . 8vo,  7  50 

Simpson,  G.     The  Naval  Constructor. .  121110,  mor.,  *5  oo 

Sinclair,  A.     Development  of  the  Locomotive  Engine. 

8vo,  half  leather,  5  oo 
Sindall,  R.  W.     Manufacture  of  Paper.     (Westminster  Series.) 

8vo,  *2  oo 

Sloane,  T.  O'C.     Elementary  Electrical  Calculations  .....  i2mo,  *2  oo 

Smith,  C.  F.     Practical  Alternating  Currents  and  Testing.  .8vo,  *2  50 

—  Practical  Testing  of  Dvnamos  and  Motors 8vo,  *2  oo 

Smith,  F.  E.     Handbook  of  General  Instruction  for  Mechanics. 

i2mo,  i  50 
Smith,  I.  W.     The  Theory  of  Deflections  and  of  Latitudes  and 

Departures i6mo,  mor.,  3  oo 

Smith,  J.  C.     Manufacture  of  Paint 8vo,  *3  oo 

Smith,  W.     Chemistry  of  Hat  Manufacturing I2mo,  *3  oo 

Snell,  A.  T.     Electrte  Motive  Power 8vo,  *4  oo 

Snow,  W.  G.     Pocketbook  of  Steam  Heating  and  Ventilation 

(In  Press.) 
Snow,  W.  G.,  and  Nolan,  T.     Ventilation  of  Buildings.     (Science 

Series.) 0 i6mo,  o  50 

Soddy,  F.     Radioactivity 8vo,  *3  oo 

Solomon,  M.     Electric  Lamps.     (Westminster  Series.) 8vo,  *2  oo 

Sothern,  J.  W.     The  Marine  Steam  Turbine 8vo.  *5  oo 


28     D.  VAN  NOSTRAND  COMPANY'S  SHORT-TITLE  CATALOG 

Soxhlet,  D.  H.     Dyeing  and  Staining  Marble.     Trans,  by  A. 

Morris  and  H.  Robson 8vo,  *2  50 

Spang,  H.  W.     A  Practical  Treatise  on  Lightning  Protection 

i2mo,  i  oo 

Speyers,  C.  L.     Text-book  of  Physical  Chemistry 8vo,  *2  25 

Stahl,  A.  W.,  and  Woods,  A.  T.     Elementary  Mechanism .  .  1 2mo,  *2  oo 
Staley,  C.,  and  Pierson,  G.  S.     The  Separate  System  of  Sewerage. 

8vo,  *3  oo 

Standage,  H.  C.     Leatherworkers'  Manual 8vo,  *3  50 

—  Sealing  Waxes,  Wafers,  and  Other  Adhesives 8vo,  *2  oo 

—  Agglutinants  of  all  Kinds  for  all  Purposes i2mo,  *3  50 

Stansbie,  J.  H.     Iron  and  Steel.     (Westminster  Series.) ....  8vo,  *2  oo 

Stevens,  H.  P.     Paper  Mill  Chemist i6mo,  *2  50 

Stewart,  A.     Modern  Polyphase  Machinery. i2mo,  *2  oo 

Stewart,  G.     Modern  Steam  Traps i2mo,  *i  25 

Stiles,  A.     Tables  for  Field  Engineers i2mo,  i  oo 

Stillman,  P.     Steam-engine  Indicator i2mo,  i  oo 

Stodola,  A.     Steam  Turbines.     Trans,  by  L.  C.  Loewenstein .  8vo,  *5  oo 

Stone,  H.     The  Timbers  of  Commerce 8vo,  3  50 

Stone,  Gen.  R.     New  Roads  and  Road  Laws i2mo,  i  oo 

Stopes,  M.     Ancient  Plants 8vo,  *2  oo 

Sudborough,  J.  J.,  and  James,  T.  C.     Practical  Organic  Chem- 
istry   i2mo,  *2  oo 

Suffling,  E.  R.     Treatise  on  the  Art  of  Glass  Painting 8vo,  *3  50 

Swan,  K.     Patents,  Designs  and  Trade  Marks.     (Westminster 

Series.) 8vo,  *2  oo 

Sweet,  S.  H.     Special  Report  on  Coal 8vo,  3  oo 

Swoope,  C.  W.     Practical  Lessons  in  Electricity .  i2mo,  *2  oo 

Tailfer,  L.     Bleaching  Linen  and  Cotton  Yara  and  Fabrics .  .  8vo,  *5  oo 
Templeton,  W.     Practical  Mechanic's  Workshop  Companion. 

i2mo,  mor.,  2  oo 
Terry,  H.  L.     India  Rubber  and  its  Manufacture.     (Westminster 

Series.) 8vo,  *2  oo 

Thorn,  C.,  and  Jones,  W.  H.     Telegraphic  Connections. 

oblong  i2mo,  i  50 

Thomas,  C.  W.     Paper-makers'  Handbook (In  Press.) 

Thompson,  A.  B.     Oil  Fields  of  Russia 4to,  *7  50 

Petroleum  Mining  and  Oil  Field  Development. 8vo,  *5  oo 


D.  VAN  NOSTRAND  COMPANY'S  SHORT-TITLE  CATALOG  29 

Thompson,  E.  P.     How  to  Make  Inventions 8vo,  o  50 

Thompson,  W.  P.     Handbook  of  Patent  Law  of  All  Countries 

i6mo,  i  50 

Thornley,  T.     Cotton  Combing  Machines 8vo,  *3  oo 

—  Cotton  Spinning 8vo, 

First  Year *i  50 

Second  Year *2  50 

Third  Year *2  50 

Thurso,  J.  W.     Modern  Turbine  Practice 8vo,  *4  oo 

Tinney,  W.  H.     Gold-mining  Machinery 8vo,  *5  oo 

Titherley,  A.  W.     Laboratory  Course  of  Organic  Chemistry. .  8vo,  *2  oo 

Toch,  M.     Chemistry  and  Technology  of  Mixed  Paints 8vo,  *3  oo 

Todd,  J.,  and  Whall,  W.  B.     Practical  Seamanship 8vo,  *7  50 

Tonge,  J.     Coal.     (Westminster  Series.) 8vo,  *2  oo 

Townsend,  J.     lonization  of  Gases  by  Collision 8vo,  *i  75 

Transactions  of  the  American  Institute  of  Chemical  Engineers. 

8vo, 

Vol.    I.     1908 *6  oo 

Vol.  II.     1909 *6  oo 

Traverse  Tables.     (Science  Series.) i6mo,  o  50 

mor.,  i  oo 
Trinks,    W.,    and    Housum,    C.      Shaft    Governors.     (Science 

Series.) i6mo,  o  50 

Tucker,  J.  H.     A  Manual  of  Sugar  Analysis 8vo,  3  50 

Tumlirz,  O.     Potential.     Trans,  by  D.  Robertson i2mo,  i  25 

Tunner,   P.    A.     Treatise    on   Roll-turning.     Trans,   by   J.    B. 

Pearse 8vo  text  and  folio  atlas,  10  oo 

Turbayne,  A.  A.     Alphabets  and  Numerals 4to,  2  oo 

Turrill,  S.  M.     Elementary  Course  in  Perspective i2mo,  *i  25 

Under  hill,  C.  R.     Solenoids,  Electromagnets  and  Electromag- 
netic Windings I2mo,  *2  oo 

Urquhart,  J.  W.     Electric  Light  Fitting i2mo,  2  oo 

—  Electro-plating i2mo,  2  oo 

—  Electrotyping I2mo,  2  oo 

—  Electric  Ship  Lighting I2mo,  3  oo 

Universal  Telegraph  Cipher  Code ".  t i2mo,  i  oo 

Vacher,  F.     Food  Inspector's  Handbook i2mo,  *2  50 


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Vai3  Nostrand's  Chemical  Annual.  Second  issue  1909  ....  i2mo,  *2  50 
—  Year  Book  of  Mechanical  Engineering  Data.  First  issue 

1910. (In  Press.) 

Van  Wagenen,  T.  F.  Manual  of  Hydraulic  Mining i6mo,  i  oo 

Vega,  Baron,  Von  Logarithmic  Tables 8vo,  half  mor.,  2  50 

Villon,  A.  M.  Practical  Treatise  on  the  Leather  Industry. 

Trans,  by  F.  T.  Addyman 8vo,  *io  oo 

Vincent,  C.  Ammonia  and  its  Compounds.  Trans,  by  M.  J. 

Salter. 8vo,  *2  oo 

Volk,  C.  Haulage  and  Winding  Appliances 8vo,  *4  oo 

Von  Georgiovics,  G.  Chemical  Technology  of  Textile  Fibres. 

Trans,  by  C.  Salter 8vo,  *4  50 

—  Chemistry  of  Dyestuffs.     Trans,  by  C.  Salter 8vo,  *4  50 

Wabner,  R.     Ventilation  in  Mines.     Trans,  by  C.  Salter.  ..8vo,  *4  50 

Wade,  E.  J.     Secondary  Batteries 8vo,  *4  oo 

Wadsworth,  C.     Primary  Battery  Ignition i2mo  (In  Press.) 

Wagner,  E.     Preserving  Fruits^  Vegetables,  and  Meat. . . .  i2mo,  *2  50 

Walker,  F.     Aerial  Navigation 8vo, 

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Walker,  S.  F.     Steam  Boilers,  Engines  and  Turbines 8vo,  3  oo 

—  Refrigeration,  Heating  and  Ventilation  on  Shipboard. 

i2mo,  *2  oo 

—  Electricity  in  Mining 8vo,  *3  50 

Walker,  W.  H.     Screw  Propulsion 8vo,  o  75 

Wallis-Tayler,  A.  J.     Bearings  and  Lubrication 8vo,  *i  50 

—  Modern  Cycles 8vo,  4  oo 

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—  Sugar  Machinery i2mo,  *2  oo 

Wanklyn,  J.  A.     Treatise  on  the  Examination  of  Milk     .  .  i2mo,  i  oo 

-  Water  Analysis i2mo,  2  oo 

Wansbrough,  W.  D.     The  A.  B  C  of  the  Differential  Calculus 

i2mo,  *i  50 

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Ward,  J.  H.     Steam  for  the  Million 8vo,  i  oo 


D.  VAN  NOSTRAND  COMPANY^  SHORT-TITLE  CATALOG     31 

Waring,  G.  E.,  Jr.     Sewerage  and  Land  Drainage *6  oo 

—  Modern  Methods  of  Sewage  Disposal i2mo,  2  oo 

—  How  to  Drain  a  House I2mo,  i  25 

Warren,  F.  D.     Handbook  on  Reinforced  Concrete i2mo,  *2  50 

Watkins,  A.     Photography.     (Westminster  Series) 8vo  (In  Press.) 

Watson,  E.  P.     Small  Engines  and  Boilers i2mo,  i  25 

Watt,  A.     Electro-plating  and  Electro-refining  of  Metals *4  So 

Watt,  A.     Electro-metallurgy i2mo,  i  oo 

The  Art  of  Paper  Making *3  oo 

The  Art  of  Soap-making 8vo,  3  oo 

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Weale,  J.     Dictionary  of  Terms  used  in  Architecture i2mo,  2  50 

Weather  and  Weather  Instruments i2mo,  i  oo 

paper,  o  50 
Webb,  H.  L.     Guide   to  the  Testing  of  Insulated  Wires  and 

Cables 1 2ino,  i  oo 

Webber,  W.  H.  Y.     Town  Gas.     (Westminster  Series.) 8vo,  *2  oo 

Weekes,  R.  W.     The  Design  of  Alternate  Current  Transformers 

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Weisbach,  J.     A  Manual  of  Theoretical  Mechanics 8vo,  *6  oo 

sheep,  *7  50 
Weisbach,  J.,  and  Herrmann,  G.     Mechanics  of  Air  Machinery 

8vo,  *3  75 
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i2mo,  *i  50 

Weymouth,  F.  M.     Drum  Armatures  and  Commutators  . .  .8vo,  *3  oo 

Wheeler,  J.  B.     Art  of  War i2mo,  i  75 

Field  Fortifications I2mo,  i  75 

Whipple,  S.     An  Elementary  and  Practical  Treatise  on  Bridge 

Building 8vo,  3  oo 

Whithard,  P.     Illuminating  and  Missal  Painting i2mo,  i  50 

Wilkinson,  H.  D.     Submarine  Cable  Laying  and  Repairing . .  8vo,  *6  oo 
Williams,  A.  D.,  Jr.,  and  Hutchinson,  R.  W.    The  Steam  Turbine. 

(In  Press.) 

Williamson,  R.  S.     On  the  Use  of  the  Barometer 4to,  15  oo 

Practical  Tables  in  Meteorology  and  Hypsometery 4to,  2  50 

Willson,  F.  N.     Theoretical  and  Practical  Graphics 4to,  *4  oo 

Wimperis,  H.  E.     Internal  Combustion  Engine 8vo,  *3  oo 

Winchell,  N.  H.,  and  A.  N.     Elements  of  Optical  Mineralogy .  8vo,  *3  50 


32     D.  VAN  NOSTRAND  COMPANY'S  SHORT -TITLE  CATALOG 

Winkler,  C.,  and  Lunge,  G.     Handbook  of  Technical  Gas-Analy- 
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Woodbury,  D.  V.     Elements  of  Stability  in  the  Well-propor- 
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Worden,  E.  C.     The  Nitrocellulose  Industry.     Two  Volumes. 

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Wright,  A.  C.     Analysis  of  Oils  and  Allied  Substances 8vo,  *3  50 

—  Simple  Method  for  Testing  Painter's  Materials 8vo,  *2  50 

Wright,  H.  E.     Handy  Book  for  Brewers 8vo,  *5  oo 

Wright,  F.  W.     Design  of  a  Condensing  Plant i2mo,  *i  50 

Wright,  T.  W.     Elements  of  Mechanics 8vo,  *2  50 

Wright,  T.  W.,  and  Hayford,  J.  F.     Adjustment  of  Observations 

8vo,  *3  oo 

Young,  J.  E.     Electrical  Testing  for  Telegraph  Engineers. .  .8vo,  *4  oo 

Zeidler,  J.,  and  Lustgarten,  J.     Electric  Arc  Lamps 8vo,  *2  oo 

Zeuner,    A.     Technical     Thermodynamics.     Trans,    by    J.    F. 

Klein.     Two  Volumes 8vo,  *8  oo 

Zimmer,  G.  F.     Mechanical  Handling  of  Material 4to,  *io  oo 

Zipser,  J.     Textile  Raw  Materials.     Trans,  by  C.  Salter 8vo,  *5  oo 

Zur    Nedden,  F.     Engineering  Workshop  Machines  and  Proc- 
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